# Seminarios

The Department of Astronomy Seminar series takes place weekly in the lecture hall of the Astronomy Department, where both guest and local scientists present new results.

If you are interested in giving a Seminar presentation please contact Nathan Leigh (nleigh [at] amnh.org). Talks should be no longer than 45 min, and present exciting new results.

The recorded talks will be available here: http://stf.astroapoyo.cl/colloquia/

#### Elisa Boera, SISSA, Italy

During hydrogen reionization the UV radiation from the first luminous sources injected vast amount of energy into the intergalactic medium, photo-heating the gas to tens of thousands of degree Kelvin. This increase in temperature has left measurable imprints' in the thermal history of the cosmic gas: a peak in the temperature evolution at the mean density and a smoothing out of the gas in the physical space by the increased gas pressure following reionization (i.e. Jeans smoothing effect). The structures of the HI Lyman-alpha forest at high redshift are sensitive to both these effects and therefore represent a powerful tool to understand when and how reionization happened. I will present the most recent constraints on the thermal history of the intergalactic medium obtained using the Lyman-alpha forest flux power spectrum at z>5. I will show how these results can be used to obtain information on the timing and the sources of the reionization process and I will discuss their consistency with different possible reionization scenarios.

Time: 12:00 hrs

#### Amy Secunda, Princeton University, USA

Stellar mass black holes (BHs) orbiting around supermassive black holes (SMBH) in active galactic nucleus (AGN) disks are possible sources for binary stellar mass black hole (BBH) mergers detected by the Laser Interferometer Gravitational Wave Observatory (LIGO) and extreme mass ratio inspirals (EMRIs) that could be detected by the Laser Interferometer Space Antenna (LISA). AGN disks are promising locations for BBH mergers because the powerful influence of the gas drives orbital evolution, makes encounters dissipative, and leads to migration. In this talk, I will first share results from simulations of BHs orbiting in the prograde direction in AGN disks performed using an augmented N-body code that includes drag and migration forces exerted by the gas. In these simulations, BBHs form rapidly as they migrate to regions of the disk where the positive and negative torque cancels out, called migration traps. Like a majority of reported LIGO detections thus far, a large fraction of the BBH mergers in these simulations have similar component masses, total mass below 100 solar masses, and small effective dimensionless spins (\chi_eff). However, these simulations also produce high total mass and uneven mass ratio mergers resembling two unusual LIGO detections GW190521 and GW190412 at a rate of ∼0.1 Gpc-3 yr-1, and ∼0.3 Gpc-3 yr-1, respectively. Additionally, some mergers could have mis-aligned spins, or negative \chi_eff. Second, I will discuss the impact of BHs that orbit in the retrograde direction in AGN disks on BBH mergers. An analytic calculation of the orbital evolution of these retrograde orbiters suggests they may not have a large effect on the overall merger rates of BHs in AGN disks and are likely to become EMRIs.

Time: 12:00 hrs

#### Ken Shen, Berkeley University, USA

In the past decade, mounting evidence has cast doubt on the standard Chandrasekhar-mass Type Ia supernova progenitor scenario. In this talk, I will discuss a new scenario, in which an explosion is triggered as two white dwarfs begin to merge. In this dynamically driven double-degenerate double-detonation (D6) scenario, the exploding white dwarf is significantly below the Chandrasekhar mass. I will present our hydrodynamical and radiation transport simulations of these explosions and show that they reproduce most of the observable features of Type Ia supernovae. I will also discuss the discovery of hypervelocity survivors that provide overwhelming evidence that the D6 scenario occurs in nature.

Time: 12:00 hrs

#### Yuan Li, North Texas University, USA

Turbulence is ubiquitous in the universe and plays an important role in diverse astrophysical processes, from star formation to galaxy evolution. Measuring turbulence in astrophysics, however, is not always easy. In this talk, I will discuss novel techniques my group recently developed in the analysis of turbulence in the interstellar medium (ISM) and the intracluster medium (ICM). We study the motions of young stars in the Orion Molecular Cloud Complex, using the full 6-dimensional measurements of positions and velocities provided by the APOGEE-2 and Gaia DR2 surveys. We compute the velocity structure functions (VSFs) of the stars in six different groups within the Orion Complex, and find that the motions of stars in all diffuse groups exhibit strong characteristics of turbulence. Our VSFs also show features supporting local energy injection from supernovae. We have also analyzed the motions of multiphase gas in the ICM of three nearby galaxy clusters: Perseus, Abell 2597 and Virgo. We show that the motions of the filamentary cool clouds are turbulent, and the turbulence is driven by feedback from the SMBHs in the centers of these clusters. The smallest scales we probed are comparable to the mean free path in the hot ICM. The detection of turbulence on these scales provides strong evidence that isotropic viscosity is suppressed in the hot plasma.

Time: 12:00 hrs

#### Rosalba Perna, Stony Brook University, USA

The observation of gravitational waves has opened a new, unexplored window onto the Universe. Among the sources of gravitational wave transients, compact objects such as neutron stars (NSs) and black holes (BHs) play the most important role. In this talk, I will focus on the expected gravitational wave signal when two compact objects (NS-NS and NS-BH) in a binary merge. These events are believed to be accompanied by a strong electromagnetic signature in gamma-rays, followed by longer-wavelength radiation. I will discuss what can be learned from the complementary observations of the electromagnetic and the gravitational wave signals during these events, with particular focus on the source GW170817/GRB170817.

Time: 12:00 hrs

#### Ciro Pinto, INAF, Italy

The detection of fully-grown supermassive black holes in active galactic nuclei at high redshift, when the Universe was young, challenges the theories of black holes growth, requiring long periods of high accretion, most likely above the Eddington limit. These objects will be difficult to probe even with future advanced observatories. Ultraluminous X-ray sources (ULXs) are nearby stellar-mass black holes or neutron stars accreting above their Eddington limit. This was understood after the discovery of coherent pulsations and cyclotron lines in some ULXs, indicating that at least a fraction of them hosts neutron stars as compact objects and, finally, our discovery of powerful winds as predicted by theoretical models of super-Eddington accreting black holes and neutron stars. ULX winds carry a huge amount of power owing to their mildly relativistic speeds (~0.2c) and are able to significantly affect the surrounding medium, producing the observed 100s pc super bubbles, and limit the amount of matter that can reach the central accretor. The study of ULX winds is therefore quintessential to understand 1) how much and how fast can matter be accreted by black holes and 2) how strong is their feedback onto the surrounding medium in the regime of high accretion rate such as for quasars and supermassive black holes at their peak of growth. I will provide an overview on this vast phenomenology and discuss how we can use similar techniques on highly-accreting supermassive black holes to understand their fast growth and feedback onto the host galaxy.

Time: 12:00 hrs

#### Taeho Ryu, John Hopkins University, USA

Tidal disruption events (TDEs) occurs when a star is tidally disrupted by a supermassive black hole. As TDEs are being detected at an accelerating rate, we will soon enter the era where demographic studies for inactive supermassive black holes are possible via TDEs. Two important characteristic scales, the tidal radius and the energy of the stellar debris, are often estimated on an order-of-magnitude basis without taking into account the star’s internal structure and relativistic effects. Since tidal disruption events take place at shorter distances for higher black hole mass, fully general relativistic calculations of tidal forces are required to study the pericenter-dependence of tidal disruption properties for a wide range of black hole mass. Using fully general relativistic hydrodynamics simulations and MESA-model initial conditions, we determine the physical tidal radii yielding full disruptions and the characteristic energy widths of the stellar debris. Furthermore, I present a new mass inference method called TDEmass, based upon a physical model for optical/UV light emission that incorporates the relativistic correction factor for the debris energy. In this model, the only two inputs are peak luminosity and blackbody temperature at peak. Since only spectral data at peak are used, no assumptions for the temporal trends of lightcurves and their relations to mass fallback rates are made. In the future, this method could be useful to study the population properties of both massive black holes and stars in quiescent galactic nuclei.

Time: 12:00 hrs

#### Nadine Neumayer, MPIA Heidelberg, Germany

The centers of massive galaxies are special in many ways, not least because apparently all of them host supermassive black holes. Since the discovery of a number of relations linking the mass of this central black hole to the large scale properties of the surrounding galaxy bulge it has been suspected that the growth of the central black hole is intimately connected to the evolution of its host galaxy. However, at lower masses, and especially for bulgeless galaxies, the situation is much less clear. Interestingly, these galaxies often host massive star clusters at their centers, and unlike black holes, these nuclear star clusters provide a visible record of the accretion of stars and gas into the nucleus. I will present our ongoing observing programme of the nearest nuclear star clusters, including the ones in our Milky Way and the Sagittarius dwarf galaxy. These observations provide important information on the formation mechanism of nuclear star clusters, allow us to measure potential black hole masses and give clues on how black holes get to the centers of galaxies.

Time: 12:00 hrs

#### Andy Longobardo, INAF-IAPS, Italy

Comets are among the most primitive bodies in the Solar System and still contain records of the physical processes occurred during the Solar System formation. In particular, cometary dust is very useful to reconstruct the history of the Solar System, because dust was the source of all Solar System bodies. The ESA/Rosetta mission (2014-2016) gave a unique opportunity to decipher the comets’ evolution, since it was the first mission to orbit a comet (i.e., 67P/Churyumov-Gerasimenko), escorting it during the main stages of its orbit, from pre-perihelion (when the comet was poorly active) to post-perihelion (when the comet surface and coma were partially renewed from the occurred activity). The seminar presents the works leaded from the speaker during the mission and during the activity of the ISSI (International Space Science Institute) International Team “Characterization of 67P/Churyumov-Gerasimenko cometary activity” (2019-2022, whose the speaker is leader).

Time: 12:00 hrs

#### Wlad Lyra, New Mexico State University, USA

The New Horizons flyby of the cold classical Kuiper Belt object MU69 showed it to be a contact binary. The existence of other contact binaries in the 1--10 km range raises the question of how common these bodies are and how they evolved into contact. In this talk I will show, considering that the pre-contact lobes of MU69 formed as a binary embedded in the Solar nebula, the subsequent orbital evolution in the presence of gas drag. While the sub-Keplerian wind of the disk is able to bring the drag timescales for 10 km bodies to under 1 Myr in the asteroid belt, at the distances of the Kuiper belt the same mechanism is rendered ineffective. Instead, a combination of nebular drag and Kozai-Lidov oscillations is a more promising channel for collapse. I will describe a solution to the hierarchical three-body problem with nebular drag that we implemented into a Kozai cycles plus tidal friction model. The permanent quadrupoles of the pre-merger lobes make the Kozai oscillations stochastic, and we find that when gas drag is included the shrinking of the semimajor axis more easily allows the stochastic fluctuations to bring the system into contact. Evolution to contact happens very rapidly (within 10,000 yrs) in the pure, double-average quadrupole, Kozai region between ~85-95 degrees, and within 3 Myr in the drag-assisted region beyond it. The synergy between the permanent quadrupole and gas drag widens the window of contact to 80-100 degrees of initial inclination, over a larger range of semimajor axes than either Kozai or J2 alone. As such, the model predicts a low initial occurrence of binaries in the asteroid belt, and an initial contact binary fraction of about 10% for the cold classicals in the Kuiper belt.

Time: 12:00 hrs

#### Marina Kounkel, Vanderbilt University, USA

Gaia DR2 provides unprecedented precision in measurements of the distance and kinematics of stars in the solar neighborhood. Through applying hierarchical clustering on 5D data set (3D position + 2D velocity), we identify a number of clusters, associations, and comoving groups within 3 kpc. Through leveraging machine learning techniques, we can estimate the ages of these stars with pseudo-isochrone fitting. Furthermore, supervised learning then allows for identification of isolated pre-main sequence stars that cannot be recovered through clustering. With these efforts combined, we can produce to date the largest catalog of stars with known ages, allowing for investigation of star formation history of the solar neighborhood, such as identifying a ring of stars with ages of up to 40 Myr tracing the outer edges of the Local Bubble that has likely been responsible for the formation of the Gould's belt. Most of the young stars are commonly found to be filamentary or string-like populations, oriented in parallel to the Galactic plane, and some span hundreds of parsec in length. Most likely, these strings are primordial, tracing the morphology of filamentary clouds that produced them, rather than the result of tidal stripping or dynamical processing. The youngest strings (younger than 100 Myr) tend to be orthogonal to the Local Arm. Stars in a string tend to persist as comoving for time scales of ~300 Myr, after which most dissolve into the Galaxy. These data shed a new light on the local galactic structure and a large-scale cloud collapse.

Time: 12:00 hrs

#### Michiko Fujii, University of Tokyo, Japan

Gaia, an astrometry satellite, has dramatically updated the dynamical structures of the Milky-Way galaxies. However, the information that we can obtain from observations are limited in terms of both time and space. We can observe only the current positions and velocities of stars within a few kpc from the Sun. On the other hand, simulations provide us the entire time evolution of modeled galaxies. We performed fully self-consistent N-body simulations of disk galaxies modeling the Milky-Way. We model galactic disk, bulge, and dark matter halo as N-body systems with maximum 8 billion particles. using the same mass resolution to avoid numerical heating. Our high-resolution simulation allows us to follow the individual orbits of stars which are trapped in the inner Lindblad resonances of the bar. Observed structures in the distribution of stars in the phase space is explained by such resonant orbits. I will also talk about the transient spiral structures of disk galaxies.

Passcode: ik9HHy

Time: 12:00 hrs

#### Cristobal Petrovich, Pontificia Universidad Católica , Chile

The flatness of the solar system led to the notion that the planets formed within a disk around the young Sun. Although this notion is broadly confirmed by images of protoplanetary disks and a population a multi-planet systems, some exoplanets challenge this flatness hypothesis, presenting significant tilts relative to either their host stars’ equators (stellar obliquities) or other planets (mutual inclinations). In this talk, I will discuss what physical processes can be responsible from these tilts and what they teach us about the history of planetary systems. First, I will focus on a population of sub-Neptune planets with large stellar obliquities and argue that their large tilts were likely imprinted early on during the evaporation of their birth disks. Second, I will focus on the question of coplanarity in Kepler planetary systems and argue that most of these systems have been subject to dynamical heating, with the hottest systems ending as ultra-short-period planets in sub-day orbits. Finally, I will discuss the prospects of using astrometric measurements from Gaia to continue providing with new clues on the flatness of exoplanet systems.

Passcode: ik9HHy

Time: 12:00 hrs

#### Floor Broekgaarden, CfA at Harvard, USA

Have you ever made a sudoku and/or played the board game battleships? If so, congratulations! - you master the basic ingredients for the statistical tools that are crucial to understand the origin of the merging black holes in our Universe! Gravitational-wave observations of binary black hole mergers are rapidly providing new insights into the physics of massive stars and the evolution of binary systems. Making the most of expected near-future observations for understanding stellar physics will rely on comparisons with simulations of binary stars. However, the vast majority of simulated binaries never produce binary black hole mergers, which makes investigating these populations computationally inefficient. This is currently one of the major barriers in our field of “gravitational-wave paleontology”. In this talk I will discuss this problem and focus on demystifying some of the state-of-the-art statistical algorithms that are being developed to overcome the computational inefficiency of our simulations. During the talk I will show the similarities between some of the algorithms and well-known puzzle strategies. In the end I will also discuss how these tools can play important roles in other fields of astronomy.

Time: 12:00 hrs

#### Evelyn Johnston, Pontificia Universidad Católica , Chile

Nuclear star clusters (NSCs) are a common characteristic of dwarf galaxies, particularly higher-mass dwarfs. There are two main scenarios discussed in the literature to explain their formation, in-situ formation and migration, and clues to the formation of an NSC lie in its SFH. However, NSC spectra are faint and their light is often contaminated by light of the host galaxy, making it difficult to truly isolate the stellar populations of the NSC itself. As part of the Next Generation Fornax Survey (NGFS), I am using BUDDI (Bulge-Disc Decomposition of IFU data) to overcome this issue. BUDDI uses information from the entire datacube to create a wavelength-dependent model of each each component within a galaxy, from which one can extract a spectrum representing purely the light from that component. In this talk, I'll introduce BUDDI and present our results from its application to a sample of Fornax dwarfs observed with MUSE. I will conclude with a discussion on the formation of NSCs and their role in the evolution of dwarf galaxies.

Time: 12:00 hrs

#### Alessandro Trani, University of Tokyo, Japan

The astrophysical origin of merging black hole binaries is still a mystery. Two main pathways are usually advocated: isolated binaries merging in the field, and dynamically interacting binaries formed in star clusters. The coarse localization of gravitational wave events cannot indicate the environment in which the binary formed, but discerning among these two scenarios can be possible via the progenitor binary parameters that are observable via gravitational wave interferometry, namely masses, eccentricity, and spin. However, present models of the aforementioned formation pathways do not indicate an appreciable difference in the mass distributions, and eccentricity is unlikely to be inferred with current ground-based detectors. On the other hand, the magnitude and orientation of black hole spins is a promising indicator of the formation history of merging binaries. Merging black hole binaries from isolated binaries will likely have spins aligned with the orbit due to tidal spin-up, while binaries ejected from star clusters will have some degrees of misalignment. We quantify the expected spin parameters distributions of black hole binaries ejected from globular and open clusters by combining population synthesis and gravitational few-body simulations. Using such information, we may be able to link black hole spin to the binary formation pathway, thus leading to a more detailed picture of theiar environment and origin.

Time: 12:00 hrs

#### Tom Richtler, Universidad de Concepción, Chile

Dust is found frequently in early-type galaxies. The traditional view that dust is produced by young stars, can only be rescued if dust in old stellar populations would have an "external origin" (whatever that means). I shall show a gallery of dust manifestations in various galaxies. A few galaxies like NGC 3311, NGC 1316 and NGC 5102 will be discussed in more detail with regard to their dust and gas content. The lesson to be learned is that apparently a significant part of the dust is produced and distributed by dusty winds from galactic nuclei.

Time: 12:00 hrs

#### Talvikki Hovatta, University of Turku, Finland

Identifying the most likely sources for high-energy neutrino emission has been one of the main topics in high-energy astrophysics ever since the first observation of high-energy neutrinos by the IceCube Neutrino Observatory. Active galactic nuclei with relativistic jets, blazars, have been considered to be one of the main candidates due to their ability to accelerate particles to high energies. In my talk, I will describe a study where we examined the connection between radio emission and IceCube neutrino events using data from the Owens Valley Radio Observatory and Metsähovi Radio Observatory blazar monitoring programs. We identified sources in our radio monitoring sample, which are positionally consistent with IceCube high-energy neutrino events. We estimated their mean flux density and variability amplitudes around the neutrino arrival time, and compared these with values from random samples to establish the significance of our results. Based on our results we conclude that although it is clear that not all neutrino events are associated with strong radio flaring blazars, when we see large amplitude radio flares in a blazar at the same time as a neutrino event, it is unlikely to happen by random coincidence.

Time: 12:00 hrs

#### Roberto Navarro, Universidad de Concepción, Chile

Remote sensing and in situ observations in the solar wind show that the particle velocity distributions usually present characteristics of systems out of thermal equilibrium. An open question is related to why minor ions such as alpha particles (He+2) flow away from the Sun faster than protons, and why minor ions are also preferentially heated to temperatures near mass proportionality. In this talk, we show that kinetic instabilities are able to enhance spontaneously thermal magnetic fluctuations, and that these fluctuations may be related to the processes leading to plasma heating and acceleration. We also show that ion-cyclotron resonances may explain the distribution of alpha heating, and the limitations of the alpha-to-proton drift at low plasma beta, as observed in the solar wind at 1 AU.

Time: 12:00 hrs

#### Viraj Manwadkar, University of Chicago and UdeC, USA and Chile

The gravitational three-body problem is one of the longest-standing open problems in physics, dating all the way back to Newton. The problem statement is quite simple: given 3 masses with their initial position and velocities, solve for the subsequent motion. Despite this apparent simplicity, an analytical solution for the three-body problem still evades us. The main reason for this is that the three-body system exhibits chaos. Even though the underlying force evolving the system is known, which is a simple 1/r^2 gravitational force, it is difficult to predict the system's future. However, with the development of computational methods that enable us to run numerical simulations, we have been able to study the general three-body problem in a statistical fashion. As a result, the focus over past few decades has been on providing a statistical description of the general three-body problem instead of an analytical one. In this talk, I will give an overview of the chaotic three-body problem from the statistical perspective and discuss some essential properties like phase space maps, lifetime distributions and ejection probabilities. I will also highlight some ongoing efforts in developing a statistical theory for the three-body problem and some preliminary comparisons between theory and simulations.

Time: 12:00 hrs

#### Ricardo Salinas, Gemini South Observatory, Chile

Not nearly as famous as Cepheids and RR Lyrae stars, Delta Scuti stars, pulsators at the intersection of the instability strip and the main sequence, will be the most numerous pulsating star to be discovered by Rubin/LSST in our Galaxy. In this talk I will discuss the role of Delta Scuti in the phenomenon of extended main-sequence turn-offs in intermediate-age Magellanic Clouds star clusters, and the unexpected behaviour of its period-luminosity relation. I will finish by introducing a new survey, the MAgellanic Delta Scuti survey (MADS), which will refresh our knowledge of these variables across the Magellanic Clouds using Blanco/DECam.

Time: 12:00 hrs

#### Megan Reiter, UK Astronomy Technology Centre, UK

Most stars and planets form in clusters/associations with hundreds of low-mass stars forming alongside each high-mass star. Stellar feedback permeates these regions and plays a central role in shaping the demographics and habitability of exoplanets. Ionising radiation from high-mass stars truncates and destroys protoplanetary disks around nearby low-mass stars, reducing the timescale for planet formation. At the same time, short-lived radioactive elements synthesised in the death of these same high-mass stars may regulate the water budget of terrestrial (Earth-like) planets. As the exoplanet community steps ever closer to detecting Earth-analogs, constraints are urgently needed to constrain the role of feedback in the environments where the majority of stars/planets form. I will talk about on-going surveys using ALMA, MUSE/VLT, and M2FS/Magellan to measure gas and stellar kinematics in order to test the role of the environment in shaping the outcome of star and planet formation.

Time: 12:00 hrs

#### Morten Andersen, Gemini South Observatory, Chile

Although substantial progress has been made over the last decades on our understanding of star formation it is mostly in terms of formation of individual isolated stars. However, we know that many stars are formed in star clusters or in clustered environments. Here, the proximity of other stars and interactions with them can alter the formation of each star and thus their final properties (e.g. their final mass). However, little is known about the formation of particularly massive star clusters and their content. This is due to a combination of limited suitable targets to observe and limited sensitivity and spatial resolution of observations. As a consequence there are limited observational constraints on cluster formation models. However, in recent years suitable candidates of massive star clusters in their formation have been found. I will present our findings for several of those covering an order of magnitude in mass. I will further discuss the end product of the star formation, the Initial Mass Function (IMF) in massive resolved star clusters. Through deep high spatial resolution imaging we have probed the low-mass content of the clusters. From this we can directly compare the derived IMF with that determined for the field and low-mass clusters. Further, through dynamic mass estimates we can determine if the clusters will remain bound or dissolve and be a component of the future field star population.

Time: 12:00 hrs

#### Silvia Toonen, Birmingham University, UK

Stars are the fundamental building blocks of galaxies and stellar clusters. They are often part of small stellar systems, such as binaries and triples in which the stars can interact with each other. These interactions give rise to some of the most energetic events in the universe, e.g. supernovae Type Ia explosions and gravitational wave sources. The advent and development of large-scale time domain surveys are revealing the existence of a large and diverse zoo of transients, but their origin or progenitor evolution is often unknown. Here, I will present our latest results regarding the evolution of white dwarf binaries and their mergers, with implications for Galactic archaeology. Secondly, I will focus on the evolution of triple star systems, their evolution, interactions and resulting transients. Even though the principles of binary evolution theory have been accepted for a long time, the evolution of triples is an uncharted territory. There is a need to understand the evolution of triples, as they are common and often invoked to explain compact and exotic binaries.

Time: 14:00 hrs

#### Floor Broekgaarden, CfA at Harvard, USA

Have you ever made a sudoku and/or played the board game battleships? If so, congratulations! - you master the basic ingredients for the statistical tools that are crucial to understand the origin of the merging black holes in our Universe! Gravitational-wave observations of binary black hole mergers are rapidly providing new insights into the physics of massive stars and the evolution of binary systems. Making the most of expected near-future observations for understanding stellar physics will rely on comparisons with simulations of binary stars. However, the vast majority of simulated binaries never produce binary black hole mergers, which makes investigating these populations computationally inefficient. This is currently one of the major barriers in our field of "gravitational-wave paleontology". In this talk I will discuss this problem and focus on demystifying some of the state-of-the-art statistical algorithms that are being developed to overcome the computational inefficiency of our simulations. During the talk I will show the similarities between some of the algorithms and well-known puzzle strategies. In the end I will also discuss how these tools can play important roles in other fields of astronomy.

Time: 14:00 hrs

#### Robi Banerjee, University of Hamburg, Germany

Magnetic fields are ubiquitous on all astrophysical scales and objects. They also permeate entire galaxies, where the energy density of magnetic fields is comparable or even larger than the thermal energy. Hence magnetic fields have an wide impact on the dynamics of the interstellar medium (ISM). For instance, they could prevent the gravitational collapse of molecular cloud cores (similar to the thermal pressure) and therefore would not allow the formation of stars. In this talk, I'll discuss how stars are formed in galaxies in the presence of strong magnetic fields.

Time: 14:00 hrs

#### Lieke van Son, CfA at Harvard, USA

Gravitational-wave detections are starting to reveal the properties of the population of merging binary blackholes (BBH). Stellar theory predicts a gap in the black hole mass function between 45 and 130 Msun, referred to as the pair-instability supernovae (PISN) mass gap. This prediction of a mass gap is remarkably robust against model variations to the extent that it could be considered among the most robust predictions from stellar theory available today. The first ten binary BBH detections already indicate a dearth of BBH mergers with component masses greater than ~45\Msun. In mere weeks, O3 will increase our sample size to approximately 50. The planned 3rd generation gravitational wave detectors are estimated to detect about 10^4 BBH mergers per year and will reveal exactly how rare these PISN mass gap events are. Since the prediction of the gap is so robust, it's lower limit could be used to constrain stellar physics. Understanding if and how BBHs with a mass in the gap can be formed is essential to understand the final stages of massive stellar evolution and the different formation channels of binary black holes. In this talk, I will explore possibilities for creating black holes with masses in the gap, and I will discuss several formation channels, ranging from dynamical interactions to isolated binary evolution including super-Eddington mass accretion onto black holes and compare their rates and predictions.

Time: 14:00 hrs

#### Alessandro Lupi, Scuola Normale Superior, Italy

FIR emission in galaxies is produced in the ISM, by dust (continuum) and metal lines as [CII] and [OIII]. FIR emission lines are considered good ISM tracers, and [CII], one of the brightest lines at all redshifts, is often used as a SFR tracer. However, while in normal star-forming galaxies the SFR-[CII] correlation is tight, recent results have shown that different ISM conditions as a low metallicity or a strong radiation field can result in significant deviations, especially at high redshift. In this talk, I will discuss how state-of-the-art numerical simulations can help addressing the reliability of [CII] (and other FIR lines) as SFR tracers, by means of self-consistent chemo-dynamical cosmological simulations of both low and high redshift galaxies.

Time: 14:00 hrs

#### Andres Escala, Universidad de Chile, Chile

The principle of similitude (Rayleigh 1915) or dimensional homogeneity, states that only commensurable quantities (ones having the same dimension) may be compared, therefore, meaningful laws of nature must be homogeneous equations in their various units of measurement, a result which was formalized in the Π theorem (Vaschy 1892; Buckingham 1914 and others). However, in many areas such as Biology, Economics or even partially in Astronomy (a sub-branch of Physics), the most fundamental empirical relations do not satisfy this basic mathematical requirement. In this talk, we show (using the Π theorem) that it is indeed possible to construct homogeneous equations to describe as diverse phenomena as the star formation rate in galaxies (Kenicutt-Schmidt Law; Astronomy) and the metabolic rates of animals (Kleiber Law; Biology), in agreement with data in the literature (Escala 2015; Utreras, Becerra & Escala 2016; Escala 2019). We illustrate the power of using these mathematically well defined relations, for example, by reducing the scatter of the galactic star formation relation in numerical simulations by 43% (Utreras, Becerra & Escala 2016), or by showing how from a corrected version of the Kleiber's Law is possible to derive the empirical relation for the total energy consumed in animal's lifespan (Atasanov 2007, Escala 2020) or animal's ontogenetic growth curves (West et al. 2002)

Time: 14:00 hrs

#### Paola Caselli, MPE, USA

All ingredients to make stars like our Sun and planets like our Earth are present in the dense (~100,000 H2 molecules per cc) and cold (~ 10 K) interstellar clouds. In these "stellar-system precursors" an active chemistry is already at work, as demonstrated by the presence of a rich variety of organic molecules in the gas phase and icy mantles encapsulating the sub-micrometer dust grains, the building blocks of planets. Here, I'll present a journey from the earliest phases of star formation to protoplanetary disks, with links to our Solar System, highlighting the crucial role of astrochemistry as powerful diagnostic tool of the various steps present in the journey.

Time: 14:00 hrs

#### Nicole Karnath, SOFIA Science Center of the NASA Ames Research Center

The earliest phases of star formation are observationally difficult to detect and physically characterize. Protostars form deeply embedded within dense envelopes of gas and dust, making the process opaque at most wavelengths. Thus, this regime was previously restricted to theoretical investigations and simulations lacking observational information. Taking advantage of powerful interferometers, the VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey in Orion revealed the highest spatial resolution images of ~300 protostars to date. In this talk I will focus on the youngest protostars known to date in the Orion Molecular Clouds that were originally identified by Herschel and classified as PACS Bright Red Sources (PBRS). I will discuss the properties of their disks, outflows, envelopes, and multiplicity. Four of the 19 PBRS have dense, irregular structures and are optically thick at 0.87-mm within the central ~100 AU, and have slow outflows (when detected). These four PBRS provide direct observations of the innermost opaque regions of collapse at the onset of protostar formation. Their densities imply freefall times of ~ 100 yr, which would make these observations extremely unlikely. Thus these sources must have either extreme dust properties, or be evolving on longer time-scales with additional support. Their Kelvin─Helmholtz times are of order several thousand years. The relative fraction of these sources imply lifetimes of ~ 6000 yr, in closer agreement with the Kelvin─Helmholtz time. In this case, rotational and/or magnetic support could be slowing the collapse. Finally, I'll discuss ongoing and future observational work to quantify rotation and B-fields in these extremely young protostars.

Time: 14:00 hrs

#### Erini Ligery Lambrides, John Hopkins University, USA

Population synthesis models of actively accreting super-massive black holes (or active galactic nuclei -- AGN) predict a large fraction that must grow behind dense, obscuring screens of gas and dust. Deep X-ray surveys are thought to have provided the most complete and unbiased samples of AGN, but there is strong observational evidence that a portion of the population of obscured AGN is being missed. In this talk, I will highlight results from my recent work on where we use a sample of AGN derived from the deepest X-ray survey to date, the Chandra 7Ms GOODS-South Survey, to investigate the nature of low flux X-ray sources. We maximize the diverse wavelength coverage of the GOODS-South field, and cross-match our objects with wavelengths from the Radio to the IR. We find the predicted column densities are on average an order of magnitude higher than the calculated column densities via X-ray detections for X-ray faint sources. We interpret our results as evidence of obscured AGN disguising as low-luminosity AGN via their X-ray luminosities. The discovery of these objects has deep implications for future X-ray surveys and X-ray AGN selection criteria. I will also touch on our current work of using this unique sample to probe long standing problems with popular SMBH-Galaxy Co-Evolution paradigms.

Time: 14:00 hrs

#### Elena Redaelli, MPE, USA

Magnetic fields are ubiquitous in the interstellar medium, and they certainly play an important role during the star formation process. However, their interplay with forces such as gravity and turbulence is a topic still under great debate, also due to the intrinsic difficulties of magnetic field observations. In this talk, I will present the polarimetric observations of the protostellar core IRAS15398 performed with the SOFIA/HAWC+ camera at 214 microns. IRAS15398 is a young class 0 object embedded in Lupus I, a cloud known to be a highly magnetised environment. In our new data, the B field appears ordered and aligned with the large-scale field of the cloud and with the outflow direction. The field lines, however, present a significant bend due to the gravitational pull. We estimate a magnetic field strength of B= 78 µG, which is expected to be accurate within a factor of two. The measured mass-to-flux parameter is λ = 0.95, indicating that the core is in a transcritical regime.

Time: 14:00 hrs

#### Pierluigi Cerulo, Universidad de Concepción, Chile

The evolution of galaxies is driven by complex physical mechanisms that may have internal or environmental origins. As time passes galaxies become less star-forming and tend to acquire elliptical or lenticular morphologies. We have embarked in a simultaneous study of morphology and star formation in cluster and field galaxies with the aim of investigating the relationships between star-formation quenching and morphological transformations as a function of environment. In this talk I shall present the results of a study conducted on galaxies in the CLASH and CANDELS surveys at redshifts 0.2 < z < 0.9. By dividing galaxies into star-forming and quiescent we find that quiescent ellipticals are more abundant in clusters than in the field. Regardless of the environment, we observe an increase in the fraction of quiescent disc galaxies at low redshifts, supporting the notion that star-formation quenching precedes morphological changes, at least at low stellar masses. Star-forming field galaxies are mostly late type discs, while in clusters they present a diverse morphological composition with a non-negligible fraction of star-forming ellipticals that is detected in low-redshift clusters. I will discuss the implications of our results in the general context of galaxy evolution.

Time: 14:00 hrs

#### Phillip Grete, University of Michigan, USA

Large scale simulations are a key pillar of modern research in many areas and require ever increasing computational resources. While the fundamental architecture of supercomputers saw little change for a long time, different novel architectures emerged in recent years on the way towards the exascale era. These include many-core processors such as the Intel Xeon Phi, FPGA accelerator cards, or GPUs for general purpose computing that can have thousands of cores per card. Until recently, each new architecture can require a separate, non-trivial rewrite of a simulation code. To circumvent this, a current goal in computational science is the creation of parallel programming paradigms for writing performance portable code: code that can run efficiently at high performance on many different supercomputer architectures. Kokkos is one example of a performance portable on-node parallel programming paradigm realized as a C++ template library. We combined Athena++, an existing radiation general relativity magnetohydrodynamics CPU code, with Kokkos into K-Athena to allow simulations to run efficiently on both CPUs and GPUs using a single codebase. I will introduce performance portability approaches, and present profiling and scaling results for multiple architecture including Intel Skylake CPUs, Intel Xeon Phis, and NVidia Volta V100 GPUs. K-Athena achieves >10^8 cell-updates/s on a single V100 for second-order double precision MHD, and a speedup of 30 up to 24,576 GPUs on Summit (compared to 172,032 CPU cores) reaching 1.94x10^12 total cell-updates/s at 76% parallel efficiency. Using a roofline analysis I will demonstrate that the overall performance is currently limited by DRAM bandwidth on both CPUs and GPUs. Based on the roofline analysis K-Athena achieves a performance portability metric of 83.1% across 5 CPU generation, 4 GPU generations, and Intel Xeon Phis. Finally, I will present the strategies we used for implementation and the challenges we encountered while attempting to achieve maximum performance on different platforms. This will support other research groups to straightforwardly adopt this approach to prepare their own methods and codes for the exascale era.

Time: 14:00 hrs

#### Tim Lichtenberg, Oxford University, UK

Because astronomical observations are ultimately limited in providing a complete picture of the exoplanetary census, a comprehensive understanding of planetary systems' formation and evolution can deliver valuable insights into key physical and chemical properties that cannot be probed by remote sensing alone. In this talk, I will discuss how the inhomogeneous enrichment of forming planetary systems with short-lived radionuclides, namely Al-26 and Fe-60, in typical star-forming environments controls the interior evolution and volatile loss of planetesimals that accrete to form terrestrial planets. Their internal geophysical evolution sub-divides rocky exoplanetary systems into distinct populations: enriched systems with Solar-like or higher levels tend to form water-depleted planets, while not- or barely-enriched systems dominantly form ocean worlds, with water levels comparable to the icy moons in the outer Solar System. This suggests a direct link between the star-forming birth environment of planetary systems and the compositional make-up and long-term evolution of rocky planets that form in them: the system-to-system deviations in the abundance of short-lived radionuclides across young star-forming regions qualitatively distinguish planetary systems' formation and evolution, and control the distribution and prevalence of terrestrial planets with Earth-like bulk compositions.

Time: 14:00 hrs

#### Aaron Geller, Northwestern University, USA

In this talk, I will give a brief overview of my research on how stellar dynamics and stellar evolution conspire to create the most interesting stars and planets. I will then discuss why you should, and how you can, visualize your N-body (and other) simulation data.

Time: 13:00 hrs

#### Giacomo Fragione, Northwestern University, USA

The recent discovery of gravitational waves has opened new horizons. Current and upcoming missions promise to shed light on black holes (BHs) of every size and neutron star (NS) physics. The astrophysical origin of these mergers is among the most puzzling open questions of our time. Two primary channels have been proposed to explain the observed population of merging BHs and NSs: field binary evolution and dynamical formation in a cluster environment. The LIGO-Virgo events have made possible to estimate rates, masses, eccentricities, and projected spins of merging compact objects for the fist time. However, neither field binary evolution nor dynamical formation can explain all of the above quantities. Observations show that about one fourth of massive stars is in triple systems, comprised of an inner binary orbited by a third companion. Despite being rarer than binaries, a large fraction of triples can merge as a result of the Kozai-Lidov mechanism, imposed on the inner binary by the field of the third companion. Within current uncertainties, triples can potentially account for most, if not all, of the observed events and future LIGO-Virgo sources. The triple scenario is definitively the third pathway to compact object mergers.

Time: 13:00 hrs

#### Ashish Mahabal, California Institute of Technology, USA

Astronomy has been transformed by our ability to take repeated images of the sky and process them in real-time, thanks to faster telescopes and internet, as well as better CCDs and processing power. This has in turn helped us gather far greater volumes of data. I will talk of the various current surveys and the forthcoming ones like ZTF and LSST, and describe how machine learning is aiding our understanding of the kinds of objects the Universe is made of.

Lugar: Auditorio, Departmento de Astronomía. Universidad de Concepción

Hora: 10:00 hrs

#### Florence Durret, IAP and UPMC, Paris, France.

The DAFT/FADA survey has studied several tens of clusters in the redshift range 0.4<z<0.9. Many of them show substructures, both in the optical and X-rays, which seem to be relatively recent infalls. The percentage of mass included in substructures is found to be roughly constant with redshift, in agreement with the results of numerical simulations.

We have also searched for extensions and cosmic filaments around these clusters, and compared the distributions of galaxies, derived from density maps, of X-ray gas, obtained with XMM-Newton data, and of the total cluster mass, computed with weak lensing. All these coincide quite well, and we thus estimated the cluster masses.

The analysis of the luminosity functions of early and late type cluster galaxies suggests that clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late-type galaxies then appear to evolve into early types, enriching the red sequence between this redshift and today.

Lugar: Auditorio, Departmento de Astronomía. Universidad de Concepción

Hora: 10:00 hrs

#### Dr. Emma Fernández Alvar, Universidad Nacional Autónoma de México (UNAM)

During the last decades, the detection of spatial, chemical and kinematical inhomogeneities in the Galactic halo favor a formation scenario in line with the current Lambda-Cold Dark Matter cosmological model. However, the formation processes are still far from being well described. Here we present an analysis of the abundances of several chemical species in high-resolution stellar spectra from the APO Galactic Evolution Experiment (APOGEE), a Sloan Digital Sky Survey sub-program. In particular, we describe the analyses performed over two halo stellar sub-populations, previously detected in the work of Nissen & Schuster (2010), and following papers, from which we infer characteristics of the initial mass function (IMF) and star formation history (SFH) from simple chemical evolution models for each of these two sub-populations. We obtain an earlier, more intense, and longer SFH, and a top-heavier IMF for the sub-population with higher alpha-to-iron ratios.

Lugar: Auditorio, Departmento de Astronomía. Universidad de Concepción

Hora: 12:00 hrs

#### Alfonso Aragón-Salamanca, University of Nottingham

There is now little doubt that Lenticular (S0) galaxies are the descendants of spiral galaxies whose star-formation ceased. In this talk I will present some of the evidence we have gathered in support of this hypothesis and the physical mechanisms driving the transformation. I will also discuss some recent and ongoing work on applying spectroscopic bulge-disk decomposition techniques to multiple IFU surveys such as MaNGA.

Lugar: Auditorio, Departmento de Astronomía. Universidad de Concepción

Hora: 12:15 hrs

#### Dr. Peter Frinchaboy, Texas Christian University

A key observable used to constrain galaxy evolution models and often explored in external galaxies is the variation of chemical abundances across galaxy disks. The Milky Way provides the one galaxy where we can study these variations in utmost detail using high resolution spectroscopy.

The Open Cluster Chemical Analysis and Mapping (OCCAM) survey aims to produce a comprehensive, uniform, infrared-based data set for hundreds of open clusters, and constrain key Galactic dynamical and chemical parameters using primarily the SDSS/APOGEE survey. Open CLusters provide the most reliable ‘age-datable’ population tracer at low latitudes. I will present current current results on galactic gradients from OCCAM and and interesting age dependent trends in open cluster neutron capture elements from OCCAM optical follow-up work.

Lugar: Auditorio, Departmento de Astronomía. Universidad de Concepción

Hora: 16:00 hrs

#### J. Christopher Howk, University of Notre Dame

The predictions of light element abundances in standard Big Bang Nucleosynthesis agree very well with astrophysical probes of primordial material, with the exception of lithium. Most of the observational constraints we have on the primordial abundance and cosmic evolution of Li comes by way of the Li abundance in stellar atmospheres, which are four times lower than BBN predictions in the WMAP-era. A broad range of potential solutions to this "lithium problem" have been suggested, from stellar astrophysics solutions (depletion of the surface Li abundances in stars) to physics beyond the Standard Model (annihilating or decaying dark matter in the epoch of BBN). We have adopted a new approach to this problem, using observations of Li in interstellar gas of low-metallicity galaxies to probe the cosmic evolution of Li. I will summarize our recent results using this approach, which leave the door open for new physics in the early Universe.

Lugar: Auditorium, Department of Astronomy. Universidad de Concepción

Hora: 11:00 hrs

Stars preferentially form in clusters rather than in isolation. Moreover, Herschel observations of clusters revealed that filaments are ubiquitous and may play a central role in star formation. But, where are the protostars located relative to the filaments, especially at very early stages of cluster formation? Previously, the faintest protostars ? low mass and/or young sources ? have been invisible to observational studies, and therefore their distribution could not be known until recent high-sensitivity, high-resolution mapping campaigns with ALMA. Here I present ALMA observations of the young protostellar cluster Serpens South where 24+ protostars are revealed. Only 6 of these sources were previously detected in continuum at millimeter wavelengths. We confirmed the thesis that the filaments provide the proper conditions for star formation, as all of the sources ? including the very faintest ? lie within the filamentary structure. Next, we analyzed the evolutionary classifications for the sources identified with Spitzer, and I will present trends of their age, mass, and distribution in the cluster. Finally, I will show that the continuum map we use for this study is only one small piece of the wealth of data we obtained with ALMA, including CO line maps that allow us to identify and measure the impact of outflows launched by the numerous protostars in this complex region.

Lugar: Auditorio, Departmento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Yun-Kyeong Sheen, Korea Astronomy and Space Science Institute

Ram-pressure stripping studies of early-type galaxies have primarily focused on the impact on their hot gaseous halos previously. Our MUSE IFU observations vividly reveal the presence of star-forming blobs, and long ionised gas tails, around an elliptical galaxy in Abell 2670. The galaxy shows disturbed faint features and a series of star-forming blobs in our MOSAIC 2 deep optical images. Thanks to the revolutionary wide field-of-view of VLT/MUSE, we could simultaneously obtain IFU spectra of the blobs and the galaxy. The stars of the galaxy show no significant rotation, and yet it contains a star-forming disk of gas that is clearly rotating. Considering the disturbed low surface brightness features, reminiscent of a post-merger galaxy, it is likely that the gas was brought into the galaxy by a recent wet merger with a gas-rich companion and the star-forming blobs may also be remnants of the merger. However, the direction of the one-sided ionised tails (pointing away from the cluster centre), combined with the tadpole-like morphology of the star-forming blobs, strongly suggests that the system is undergoing ram pressure from the intracluster medium. The material in the ionised tail maintains a clear signature of the rotation of the star-forming gas disk found at the galaxy's center. In this talk, we will present how our preliminary analysis may support a scenario in which an elliptical galaxy had undergone a wet merger, which is then subjected to ram pressure stripping.

Lugar: Auditorium, Department of Astronomy. Universidad de Concepción

Hora: 11:00 hrs

Room: Auditorium, Department of Astronomy. Universidad de Concepción

Time: 15:00 hrs

#### Jorge Melnick, ESO

A raging debate dominated extragalactic astronomy in the 1970's and 80's. One camp, led by Gerard de Vaucouleurs of the Unviersity of Texas - the H0=100 camp - argued for a high value, and the other, championed by Edwin Hubble's successor, Alan Sandage at Carnegie - the H0=50 camp, argued for a low value. The discrepancy was fundamental: the high value implied an age of the universe lower than the ages of the oldest stars in our Galaxy, so H0 was one of the main drivers for the HST. And indeed HST settled the issue through observations of Cepheids in galaxies only one wrung away in the cosmic distance ladder from pure Hubble flow. Not surprisingly, the agreed value is just about exactly in between Sandage and deVaucouleurs and the cosmological constant finally settled the issue of the age discrepancy.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 11:00 hrs

#### Anatoly Miroshnichenko, University of North Carolina at Greensboro

FS CMa type stars is a group of objects with the B[e] Phenomenon. Their nature and evolutionary status are not very clear yet. Recently international efforts resulted in discovery of several binary systems among the group members. I will review current understanding of the group, present the most significant results, and compare their properties with those of other stellar groups.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 11:00 hrs

#### Sergio Torres-Flores, Universidad de La Serena

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Volker Perdelwitz, Hamburg Observatory

The proposed existence of a large ninth planet in the outer solar system has intensified search efforts for trans-neptunian objects (TNOs) both via new observations and archival data analysis. However, so far the object has eluded detection. We present a novel approach to moving object detection capable of analyzing huge amounts of archival data in order to detect TNOs and determine their orbital parameters.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Tjarda Boekholt, UdeC

The slingshot mechanism provides a new framework for understanding star (cluster) formation. I will give a brief overview of this theory and present on-going research, which has already led to the first numerical investigation on the dynamics of young stars in an oscillating gas filament (see https://arxiv.org/abs/1704.00720 ).

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Stefano Bovino, Hamburg Observatory/University of Hamburg

While we know where stars form, we do not know how this process takes place. It is well established that the rate of star formation in nearby Galaxies is surprisingly low, and the same appears to be true when we scrutinize nearby molecular clouds within our own Galaxy. That is, star formation in the local Universe is inefficient, yet we do not know why. Meanwhile, the star formation problem demands that we tackle many orders of magnitude in spatial scales (from 10 kpc down to ~1000 AU), temperatures (10 K to > 104 K), and in density. Astrochemistry accesses these regimes as well as fundamental physical quantities such as time-scales. And it is now undergoing an awakening'' driven by the dire need to develop robust theoretical frameworks within which to interpret new empirical data from cutting edge telescopes (such as ALMA, APEX, and in the near future the CST). My research focuses on the development of state-of-the-art chemical models, applicable to different environments, that allow for the interpretation of the observational data in terms of fundamental physical quantities. I will present our new model targeting the study of [CII] in nearby galaxies and show how we recover the Schmidt-Kennicutt relation in isolated gas-rich galaxy simulations. Zooming in to small scales, I will present 3D magneto-hydrodynamical simulations of collapsing clouds discussing the role of deuterium fractionation as a chemical clock. The increase in the deuterium fraction in dense star forming regions has long been proposed as a proxy to differentiate between the different evolutionary stages of the star formation process. I will show that deuteration is rather efficient in fully depleted cores leading to high deuterium abundances (in agreement with observations) within roughly a free-fall time. This theoretical astrochemistry framework will be essential for exploiting the current flood of observations of chemical tracers in environments both near and far.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Karina Voggel, ESO/University of Utah

Ultra-Compact Dwarf Galaxies (UCDs) have filled the void between classical globular clusters and dwarf galaxies in the scaling relations of early type systems. The nature of these objects is still under debate. They are either the surviving nuclei of tidally stripped dwarf galaxies or the high mass end of the globular cluster mass function. Several studies show that the dynamical mass of UCDs is elevated compared to what is expected from their stellar population. One explanation for these elevated mass-to-light (M/L) ratios is the presence of a super massive central black hole (SMBH) that is expected if they are stripped nuclei. Recently, a SMBH was detected in the Virgo cluster UCD M60-UCD1 (Seth et al. 2014). This SMBH makes up 15% of the mass of the UCD. This discovery is the clearest indication yet that UCDs originate from more massive progenitors. The elevated dynamical M/L ratios of massive UCDs suggests that more UCDs host SMBHs. Thus UCDs could contribute significantly to the overall census of black holes in galaxies. I will present the results from a follow-up effort to resolve the kinematic signatures of the very centers of several UCDs in Centaurus A and the Virgo Cluster. We use adaptive optics supported spectroscopy with SINFONI to probe them for the presence of a SMBH in their centers. We created a grid of Jeans Anisotropic Models (JAM) to find the best fit dynamical model to our data and the best-fit black hole masses. This allows us to make a first tentative estimate of the SMBH occupation fraction in UCDs.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### María José Maureira, Yale University

Nearly all stages of the star formation process have been observed in large samples and compared to theoretical predictions. However, one stage remains unobserved: the first hydrostatic core (FHSC or first core). The first core is a short-lived object in quasi-hydrostatic equilibrium that forms at the center of a collapsing core before the formation of a protostar. Observational evidence of the FHSC is of prime importance in our understanding of the early evolution of dense cores, protostars and circumstellar disks. I will present molecular line observations of first cores candidates that reveal the kinematics of the surrounding gas at 1000 AU scales. Our analysis provide strong evidence that one of the sources (L1451-mm) is indeed at a very early stage of evolution, making the best candidate for being a bona fide first core. In addition, we find that the structure and velocity field of the infalling gas of another candidate is consistent with turbulent core collapse, further showing that first core candidates are an ideal astrophysical laboratory for probing the initial conditions of low-mass star formation. I will highlight how future observations could help us to further reveal the evolutionary state of these sources as well as provide evidence that can test the predictions of (and set strong constraints on) numerical simulations of core collapse and protostar formation.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Matias Blana (OPINAS, MPE)

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Jorge Melnick (TBC)

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

Using data from the core of 47 Tuc in the ultraviolet (UV), we have identified various stellar populations in the CMD, and used the effects of mass segregation on the radial distribution of these populations to find estimates for the masses of stars at different post-main-sequence evolutionary stages. We take samples of main-sequence (MS) stars at different magnitudes (i.e., different masses), and use the effects of this dynamical process to develop a relation between the radial distance (RD) at which the cumulative distribution reaches the 20th and 50th percentile and stellar mass. Using the same data set and mass estimation technique we also study the evolution and origin of Blue Straggler Stars (BSS) in the core of 47 Tuc. t.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Eleonora Sani

Two main physical processes shape the nuclear regions in active galaxies: an intense star formation (which can be as powerful as a starburst) and an active galactic nucleus. While the existence of a SF-AGN connection is undisputed, still it is not clear which process dominates the energetic output in both local and high redshift Universe. Moreover, there is no consensus on whether AGN fuelling is synchronous with SF or follows it during post-starburst phase, or on how and when feedback processes are in action.

Here I first review how to disentangle the relative SF-AGN contribution to the energetic output of the galaxy, then I focus on the physical and geometrical properties of the circumnuclear environment.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Joris Vos

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Steven Majewski

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a large-scale, systematic and homogeneous spectroscopic census of the stellar populations of the Milky Way. Because it samples stellar spectra at infrared wavelengths (from 1.51-1.68 ?m), APOGEE is able to peer through the veils of dust that obscure and hinder traditional optical wavelength surveys to create the most comprehensive spectroscopic probe of all parts of our home Galaxy. Moreover, because the APOGEE spectra are of high resolution (R ~ 22,500), have high S/N and include time series information via repeat visits to stars, this database is being applied to numerous, wide-ranging problems in Galactic astronomy, stellar populations, stellar astrophysics and even the study of exoplanets. Operating from 2011-2014 as part of the Sloan Digital Sky Survey III (SDSS-III), and now continuing as “APOGEE-2” in SDSS-IV, the APOGEE project has already amassed over a million spectra from its northern spectrograph attached to the Sloan 2.5-m Telescope at APO in New Mexico, and will soon begin collecting data for stars in the Southern Hemisphere with the imminent installation of a twin spectrograph attached to the du Pont 2.5-m Telescope in Chile. I will summarize some science highlights from the APOGEE project, including measurements of Galactic dynamics, age and multi-element atomic composition maps for stars across the Galaxy, and the discovery and characterization of substellar mass companions and rare species of stars. I will also give an update on the southern, “APOGEE-2S” program and current plans for the APOGEE instruments for ?After Sloan IV?

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 15:00 hrs

#### Nikolaus Vogt (Universidad de Valparaíso)

The ex-nova RR Pic presents a periodic hump in its light curve which is considered to refer to its orbital period. Analyzing all available epochs of these hump maxima in the literature, and combining them with those from new light curves obtained in 2013 and 2014, we could establish a unique cycle count scheme valid during the past 50 years, and derived an ephemeris with the orbital period 0.145025959(15) days. The O – C diagram of this linear ephemeris reveals systematic deviations which could have different causes. One of them could be a light-travel-time effect caused by the presence of a hypothetical third body near the star/brown dwarf mass limit, with an orbital period of the order of 70 years. We also examine the difficulty of detecting sub-stellar or planetary companions of close red-dwarf white-dwarf binaries (including cataclysmic variables), and discuss other possible mechanisms responsible for the observed deviations in O – C. In addition, we found evidence of sporadic superhumps in RR Pic, in two epochs.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Evelyn Johnston/Boris Haeussler (ESO)

Evelyn: With the availability of large integral-field unit (IFU) spectral surveys of nearby galaxies, there is now the potential to extract spectral information from across the bulges and discs of galaxies in a systematic way. This information can address questions such as how these components built up with time, how galaxies evolve and whether their evolution depends on other properties of the galaxy such as its mass or environment.

Boris: The build-up of the galaxies that populate the red sequence today from the star-forming galaxies in the ‘blue cloud’ is the key to understanding how those most massive galaxies form. Several processes have been suggested for the transformation of blue, star-forming galaxies into the red sequence galaxies, e.g. major and minor mergers, SF quenching and in-situ star-formation, which can all move and add mass to the red sequence as a whole. Each of these processes leaves a characteristic imprint on the galaxy light and colour profiles. In order to identify the importance of these different processes, both the identification of the respective samples and the accurate measurement of their properties is vital.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 15:30 hrs

#### Richard Lane (PONTIFICIA UNIVERSIDAD CATOLICA)

The Monoceros Ring (MRi) could be a giant tidal stellar stream encircling the Milky Way disc. However, no progenitor has been uncovered and it could be something else entirely. Several years ago the globular cluster IC 4499 was reported to have a radial velocity consistent with MRi stars. This lead me to ask myself “could this cluster have come from the progenitor of the MRi?” Along the way this question lead me to other ideas with regard to the MRi and the possibility of uncovering its origins once and for all.”

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Amelia Stutz (Universidad de Concepción)

We argue that Orion hosts a fundamentally different mode of star cluster formation relative to the nearby clouds (e.g., Taurus) that have been studied to death. By comparing 3 constituents of the high-mass Orion A molecular cloud (gas, protostars, and pre-main-sequence stars), both morphologically and kinematically, weshow the following. Essentially all of Orion A’s Integral Shaped Filament (ISF) protostars lie superposed on the ISF, while almost all pre-main-sequence stars are not. The kinematics of the two populations imply that a “Slingshot” mechanism may eject protostars from their dense filamentary cradle. The ISF’s observed undulations (spatial and velocity) and previous star cluster formation episodes suggest that repeated propagation of transverse (or torsional) wavesthru the filament gas is progressively digesting the cloud. Combined with previous observations of the magnetic field, we suggest that the ISF transverse waves are magnetically induced. The presence of straight filaments in low mass systems (e.g., Taurus and L1641) as well as in turbulence simulations both with and without the inclusionof B-fields can be interpreted as follows: that low-mass cloud evolution is not fundamentally driven by B-fields. Furthermore, this theoretical clash is a clear exposition of the fact that today we simply do not have a robust theoretical scenario for the formation and evolution mechanisms for star-forming filaments that pervade allmolecular clouds. Nevertheless, in contrast to the low mass systems, the observed properties of the ISF lead to the following conclusion. The key physical difference in Orion is that it is massive enough to have survived initial star formation episode, allowing the ISF to undergo internal evolution leading to concentration of B-fields confined by a deep gravitational potential well, ultimately resulting in star cluster formation. This new picture, while consistent with previous observational and theoretical understanding, must be put to the most stringent tests. I will describe initial theoretical, modeling, and observational efforts (including ALMA results) aimed at testing the Slingshot paradigm.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Francesco Mauro (Universidad de Concepción)

When they are established with sufficient precision, the ages, metallicities and kinematics of Galactic globular clusters (GGCs) can shed much light on the dynamical and chemical evolution of the Galactic halo and bulge. While the most fundamental way of determining GC abundances is by means of high-resolution spectroscopy, in practice this method is limited to only the brighter stars in the nearest and less reddened objects. This restriction has, over the years, led to the development of a large number of techniques that measure the overall abundance indirectly from parameters that correlate with overall metallicity. One of the most efficient methods is measuring the equivalent width (EW) of the calcium II triplet (CaT) at lambda ~ 8500 Å in red giants, which are corrected for the luminosity and temperature effects using the V magnitude differences from the horizontal branch (HB). A similar method was established in the near-infrared (NIR), by combining the power of the differential magnitudes technique with the advantages of NIR photometry to minimize differential reddening effects. We used the Ks magnitude difference between the star and the reddest part of the HB (RHB) or of the red clump (RC) to generate reduced equivalent widths (rEW) from previously presented datasets. Then we calibrated these rEW against three previously reported different metallicity scales; one of which we corrected using high-resolution spectroscopic metallicities.

We calculated the calibration relations for the two datasets and the three metallicity scales and found that they are approximately equivalent, with almost negligible differences. The comparision between our NIR calibrations and the corresponding optical ones shows that they are equivalent, suggesting that the luminosity-corrected rEW using the Ks magnitude is compatible with the one obtained from the V magnitude. Subsequently the metallicities obtained from the calibration were used to investigate the internal metallicity distributions of the GCs.

We have noted that the ([Fe/H]:rEW) relation could be independent of the magnitude used for the luminosity correction and find that the calibration relations change only slightly for different metallicity scales. The CaT technique using NIR photometry is thus a powerful tool to derive metallicities. In particular, it can be used to study the internal metallicity spread of a GC. We confirm the presence of at least two metallicity populations in NGC 6656 and find that several other GCs present peculiar metallicity distributions.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Nicolás Tejos (Millenium institute of astrophysics)

I will present observational results on the large-scale connection between the intergalactic medium (IGM) and galaxies at the second half of the history of the Universe. These results come from one of the largest samples of neutral hydrogen (HI) absorption lines and galaxies in the same volume to date, obtained from deep spectroscopic galaxy surveys (VLT/VIMOS, Gemini/GMOS, Keck/DEIMOS) around QSOs having high resolution UV spectroscopy (HST/COS, HST/FOS). By comparing the HI-galaxy two-point cross-correlation with both the galaxy-galaxy and the HI-HI two-point auto-correlations, as a function of different gas/galaxy properties, we can constraint the overall statistical relationship between the IGM and galaxies on Mpc scales. I will also (briefly) describe complementary studies aimed to characterize the properties of the IGM in three distinct cosmic environments: (i) galaxy voids, (ii) filaments connecting galaxy clusters, and (iii) galaxy clusters.

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Makoto Uemura (Hiroshima University)

Sparse modeling is a framework which exploits the “sparsity” of information. This new concept has received attention in information science in the last decade, and now in astronomy. In my talk, I introduce our recent works related to the sparse modeling. The application to the power-spectrum estimation enable us to eliminate aliases and white noise for periodic variables. It can be a super-resolution technique for the image reconstruction of radio interferometer. The application to Doppler tomography is introduced as an example of the usage of sparsity in the gradient domain of images. Finally, I talk about the modeling of the peak magnitude of Type-Ia supernovae as a problem of the data-driven variable selection

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 14:00 hrs

#### Daniel Whalen (University of Portsmouth)

Primordial stars formed about 200 Myr after the Big Bang, ending the cosmic dark ages. They were the first, great nucleosynthetic engines of the universe and may be the origins of the supermassive black holes (SMBHs) found in most massive galaxies today. In spite of their importance to the evolution of the early universe not much is known for certain about the properties of Pop III stars. But with the advent of JWST, Euclid, WFIRST and the ELTs it may soon be possible to directly observe their supernovae in the NIR and thus unambiguously constrain the properties of the first stars. I will present radiation hydrodynamical calculations of the light curves of the first SNe in the universe and discuss strategies for their detection. I will also describe how some may already have been found in surveys of galaxy cluster lenses such as CLASH, Frontier Fields and GLASS. I will conclude my talk with new calculations of the evolution and collapse of supermassive primordial stars that reveal the masses of the first quasars at birth.

Lugar: Meeting Room, Department of Astronomy. Universidad de Concepción

Hora: 11:15 hrs

#### Alex Gormaz-Matamal (Universidad Católica de Valparaíso)

Massive stars are important because they enrich the ISM with their powerful stellar winds

An accurate characterisation of the winds of these stars (called line-driven winds) is importan because wind plays a key role aiming to understand better how massive stars will evolve throug their future stages, and how they contribute with the chemical enrichment and evolution of the galaxy.

Many parameterisations have been done to line-driven winds under the m-CAK theory. They have made big efforts to describe the wind, both under LTE and non-LTE conditions. However, they have not included self-consistent models taking in count hydrodynamics, and also neglect the effects of the ionisation density (fast solutions). Here, we present solutions to the line-force parameters (k, α, δ) found to line-driven winds in a self-consistent performance with the wind hydrodynamics, under LTE conditions. Hydrodynamic models are provided by the code HydWind, which are generated in an iterative way. We evaluate these results with those ones previously found, focusing in what regions of the optical depth are used to do the calculations. The values for mass-loss rate and terminal velocity obtained from our calculations are also presented. We also examine how far change the solutions when effects of ionisation density are reckoned in (delta-slow solutions).

Lugar: Auditorio, Departamento de Astronomía. Universidad de Concepción

Hora: 16:00 hrs

#### Tim de Zeeuw (Dir. Gral. ESO)

ESO is an intergovernmental organisation for astronomy founded in 1962 by five countries. It currently has 15 Member States in Europe with Brazil poised to join in the near future. Together these countries represent approximately 30 percent of the world’s astronomers. ESO operates optical/infrared observatories on La Silla and Paranal in Chile, partners in the sub-millimetre radio observatories APEX and ALMA on Chajnantor and has started construction of the Extremely Large Telescope on Armazones near Paranal. The colloquium will provide an overview of the ESO programme, with emphasis on recent developments, and will briefly touch on opportunities

Hora: 15:00 hrs

#### Bruno Dias (ESO)

There are two ways to study galaxy formation and evolution. One is to observe a large number of galaxies in different redshifts but with low spatial resolution, and the other is to observe only a few nearby galaxies, but in very much detail throughout their whole history. Globular clusters in the Milky Way are perfect targets to follow-up the second method, as their ages can be put in a timeline that tells the history of the Milky Way formation and early evolution. In this talk we will present how the chemical contents of these clusters are placed in this timeline, and what kind of information they bring about the merger of dwarf galaxies (or initial building blocks) with our Galaxy. The results from the FORS2/VLT survey of Milky Way globular clusters will be shown, in particular to release a new homogeneous metallicity scale covering the full range of metallicities of globular clusters in the Galaxy, -2.4 < [Fe/H] < 0.0. For the first time we present homogeneous abundances and atmospheric parameters of almost 800 red giant stars in 51 clusters.

Lugar: Auditorium Astronomy

Hora: 14:00 hrs

#### Jennifer Schober (Nordita, Stockholm, Sweden)

Magnetic fields are omnipresent in local galaxies and influence many processes like for example star formation crucially. The proposed generation mechanisms of magnetic seed fields, however, yield strengths of typically only 10^{-20} G or below. We propose that the small-scale dynamo plays a key role in amplifying the latter up to field strengths of 10^{-5} G which are observed in galaxies today. In my talk I will introduce the theoretical basics of the turbulent small-scale dynamo and sketch our recent progress in describing it analytically and numerically. Our semi-analytical models of young galaxies show that the dynamo builds up equipartition magnetic fields by randomly stretching, twisting, and folding the field lines within only 4 to 270 Myrs. Based on these studies we expect galaxies to be strongly magnetized from early on. A test of our proposed scenario for magnetic field evolution might be possible with future radio telescopes. I will present a model for the dependency of the cosmic ray spectrum on redshift with which I predict the synchrotron emission from highly magnetized galaxies at early times.

Lugar: Auditorium Astronomy

Hora: 14:00 hrs

#### Michael Fellhauer (UDEC)

Stardate 2009: We embarked on a mission, to boldly go where almost no man has gone before. We are investigating the formation and survival of young star clusters with methods which focus on the exact dynamics (direct N-body treatment) of the newborn stars with simplified models. The prime directive of our mission is to disentangle the influence of the different physical processes by simulating them one by one in a multitude of simplified simulations instead of producing only a few kitchen-sink models.

Lugar: Auditorium Astronomy

Hora: 14:00 hrs

#### Giovanni Carraro (ESO)

CW Leo is an archetypal carbon rich Asymptotic Giant Branch (AGB) star (carbon star). It has many strong millimeter molecular emission lines and has served as the main test bed of circumstellar envelop (CSE) research for decades Although carbon stars are usually strong pulsating stars, temporal variability of their circumstellar millimeter lines is difficult to observe. In this talk, I will present our results of the first intensive monitoring of millimeter lines toward CW Leo. With relative calibration approaches, variability in line strength has been discovered in eight groups of lines. Prominent line shape variation is also found for the two candidate maser lines SiS J=14-1 and HCN nu_2=1^f J=3-2. The first ever set of millimeter-line light curves shed new light on the properties of the dynamical atmosphere of the carbon star and millimeter maser line pumping mechanism in its CSE.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Daniel Faes (ESO)

Be stars are main-sequence fast-rotating stars that display a circumstellar emission. This emission is regarded as originated from a disk, formed by episodic mass-loss episodes from the star. Here I report our observational campaign of the Be star Achernar in its current active phase, that started in 2013 after a period of 6 years in a disk-less quiescent phase. Our dataset includes spectroscopy, broad-band polarimetry and optical long baseline interferometry – a technique capable of resolving stars and their circumstellar environments at the milliarcsecond (mas) resolution level. Using VLTI AMBER and PIONIER data, we report the first spectro-interferometric follow-up of the evolution of a Be disk. These data are interpreted in the light of the VDD (Viscous Decretion Disk) model and radiative transfer simulations of the HDUST code. I will comment on this and other modeling efforts currently being in development at the BeACoN group at the IAG-USP (Brazil), such as the BeAtlas project, which aims at understanding the rich Be phenomenology and the physical processes driving it.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Matthieu Bethermin (ESO)

The South Pole Telescope unveiled a population of dusty, star-forming galaxies magnified by strong galaxy-galaxy lensing. We determined the redshift of 39 of these sources through ALMA millimeter spectroscopy and found a median redshift of 3.9 and a maximum of 5.8. An ongoing ALMA program targeting the reddest SPT sources should find even higher redshift. This sample of strongly magnified objects at high redshift offers a unique opportunity to study the cold interstellar medium (ISM) of distant galaxy. In addition, models predict that this population should contain a mix of starbursts and massive main-sequence galaxies. I will review the main results of the SPT collaboration about the properties of the ISM of these galaxies. Fine structure lines are also a very promising tracer of the ISM of these high-redshift objects. I will present a pilot study based on SPT2132-58 for which 3 fine-structure lines were detected ([NII], [CII] and [CI]. This extreme starburst at z=4.77 has an extremely short depletion timescale of 37 Gyr with a relatively mature ISM. Explaining the existence of so evolved galaxies at such high redshifts will by a stimulating challenge for galaxy evolution models.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 12:00 hrs

#### Tom Richter (Universidad de Concepción)

While dark matter is an indispensable ingredient in standard theories of cosmological structure formation, the direct evidence for dark matter through the dynamics of galaxies leads to confusion. The flat rotation curves of spiral galaxies can hardly be understood without dark matter, if one wants to avoid modifying gravity. The situation for elliptical galaxies is more complicated because of the missing disk symmetry. One has to analyse the integrated light along an extended line of sight and for larger radii has to rely on dynamical tracers like globular clusters and planetary nebulae. I summarize our present knowledge of dark matter in elliptical galaxies in various environments from central cluster galaxies to isolated ellipticals. There is evidence that the MONDian phenomenology of galaxy dynamics also extends to elliptical galaxies. I introduce our programme of investigating isolated elliptical galaxies and present first results which are difficult to reconcile with the standard theory of galaxy formation in dark matter halos.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 12:00 hrs

#### Baitian Tang (Universidad de Concepción)

We explores several existing challenges of evolutionary stellar population synthesis models in integrated light: age-metallicity degeneracy, initial mass function (IMF), elemental abundances, and compositeness. First, we search for age-sensitive and metal-sensitive colors in three photometric systems. We also add to the discussion of optical to near-infrared Johnson-Cousins broad band colors, finding a great decrease in age sensitivity when updated isochrones are used. Then we investigate the element abundances and compositeness of our models, in which we assume a single-peak abundance distribution and the same elemental abundance trends as the Milky Way bulge stars. Varying the width of the abundance distribution function reveals novel “red lean” and “red spread” effects. Next, we study three effects that co-determine the dwarf/giant ratio: the IMF slope, the IMF low mass cut-off (LMCO), and AGB star contributions. This degeneracy can be lifted for old, metal-rich stellar populations, although at an observationally challenging level. Finally, we select and reduce more than 200 red galaxy spectra whose redshifts are around 0.4 from the DEEP2 sky survey, and measure the Lick-style spectral indices from the composite spectra. Multiple optical IMF-sensitive indices apparently suggest a shallower IMF, but it may not be astrophysical, due to possible over-abundant late-type galaxies in our sample.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Patricia Bessiere (Universidad de Concepción)

lthough there is a growing acceptance that active galactic nuclei (AGN) play an important role in the evolution of galaxies, the means by which they are triggered is still a matter of hot debate. In terms of the most luminous AGN (quasars), it has been suggested that they are triggered in major, gas-rich mergers. If this is the case, then we would expect to find clear evidence of these mergers in the form of morphological disturbance of the quasar host galaxies. However, tidal features will not be the only consequence of such mergers. It is predicted that they will also be accompanied by a prodigious burst of star formation. I will present both optical imaging and spectroscopic observations, aimed at exploring these prediction, which suggest that this merger induced scenario is indeed plausible

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Aeree Chung (Yonsei University)

Pending.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 15:00 hrs

#### Paula Jofre (Cambridge)

With less than a year to come for the first data release of Gaia, thousands of stars observed with high-resolution spectra are nowadays available. In this talk I will present our current efforts in defining and analysing the pillar calibrators of Gaia and its complementary spectroscopic survey Gaia-ESO. I will then present applications using these calibrator pillars to find stellar twins in spectroscopic surveys. Twins can be used to determine model-independent distances, making them excellent candidates to complement Gaia in the near future.

Lugar: Auditorio Facultad Ciencias Físicas y Matemáticas (first floor)

Hora: 14:00 hrs

#### Tanio Diaz Santos (Universidad Diego Portales)

Luminous and Ultra-luminous Infrared Galaxies ((U)LIRGs) represent the most important galaxy population at z > 1 as they account for more than 50% of all star formation produced in the Universe at those epochs, and encompass what it is called the main-sequence (MS) of star-forming galaxies. Investigating their local counterparts –low luminosity LIRGs– is therefore key to understand the physical properties of their interstellar medium (ISM) – a task rather challenging in the distant Universe. The Great Observatories All-sky LIRG Survey (GOALS) is a complete, 60μm selected sample of all nearby LIRGs and ULIRGs that aims to provide a panchromatic understanding of the most obscured star formation and active galactic nuclei (AGN) in the local Universe, and serve as a benchmark for comparisons with IR-bright galaxies detected in cosmological surveys. As such, one of the main aims of the GOALS project is the characterization and quantification of the IR compactness and size of the ongoing nuclear star formation in a statistical manner, and how they relate to the gas and dust properties of LIRGs. In this talk I will present Spitzer/IRS mid-IR spectroscopy and far-IR line emission observations ([CII]158μm, [OI]63μm, [OIII]88μm and [NII]122μm) obtained with Herschel/PACS for the GOALS sample, which have allowed us to identify a connection between the compactness of the starburst and other important galaxy properties, such as the total IR luminosity, AGN activity, merger stage, or dust temperature and optical depth – parameters that are thought to control the life cycle of galaxies moving in and out of the MS, locally and at high-z.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Pablo García (Universidad de Colonia)

In the galactic center, several bubble-like and arc-like structure are seen. Some of these structures are closely related to massive star cluster or SNRs, such as the “Radio Arc Bubble” located south from the Quintuplet Cluster and thougth to be produced by the interaction of the molecular materia wiht several supernova explosions or the arched- filaments which are arc-ñike structures that originated presumably fron the interaction of the gas whit the radiation fields of the massive arches cluster. In this going project, we aim to determine the excitation source and physical condition of the gas in the Arched- Filament . For this purpose, we model the submilliters and milliter emissions of the amin cooling lines of the ISM (CO (4-3), [CI] (1-0), [CI] (2-1), and [CII], detected at the filaments and nearby positions, in the contex of the Protons – Dominated Regions (PDRs) using the KOSMA -tau PDR model of clumpy clouds. The theorical predictions in Abel at aal, . (2005) to disentangle the [CII] emission originated within H II regions, and traced by [NII]observations at 205 um, from the originated within PDRs is aldo explored.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 15:00 hrs

Active galactic nuclei (AGN) are the manifestations of accretion onto the supermassive black hole in the centre of a galaxy. AGN are the most powerful, long-lived objects in the Universe and thought to play a major role for galaxy evolution. A toroidal distribution of molecular gas and dust is a key component in our current picture of active galactic nuclei. This so-called “molecular torus“ is held responsible for the orientation dependent obscuration of the central engine, and it plays a fundamental role for the accretion onto the supermassive black hole. The thermal emission of dust is one of the main possibilities to study this dusty torus. Observations using interferometry in the infrared have, in the last ten years, resolved and characterised this emission beyond simple fits of spectral energy distributions, leading to a great leap forward in our view of the dusty material surrounding AGN. I will present the most recent results of such observations, especially with mid-infrared interferometry. More than 25 active nuclei could be observed with MIDI, showing that the dust distributions are parsec sized. The sizes roughly scale with the square root of the luminosity, albeit with a much large scatter than in the near-infrared. Detailed studies of a few well resolved sources, among them the illustrious nuclei of NGC1068 and the Circinus galaxy, show a two component structure: an inner disk-like emission region which is surrounded by a polar elongated emitter. The latter shows differential absorption in line with the one-sided ionisation cones observed in the optical. These results are in qualitative agreement with recent hydrodynamic simulations of AGN tori. In general, they confirm the concept of a dusty obscurer providing viewing-angle dependent obscuration of the central engine.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Thomas Ruvinius

I will briefly introduce Be stars as objects and then continue to review the evolution of the field and its most important links to general astrophysics. For the central objects, the question of how close to critical the stellar rotation rates is coming to a consensus again. An interesting new evolution is the discovery of several stars with a variable vsini parameter, which points to rapid changes of the angular momentum content of the uppermost layers of the stellar atmosphere. Furthermore, with several large projects concluded, the questions of stellar pulsations and magnetic fields in Be stars have been answered, although work remains concering the details. A newly opened question is the chemical abundance enhancement of Be stars due to rapid rotation, that seems not to be present as predicted by current models. Concerning the circumstellar disk, the models are now sufficently evolved to reproduce the temporal behaviour of disks in built-up and decay. Although the models do reproduce the observations, a surprisingly high viscosity is required. Such a high value lacks an explanation, considering currently known sources of viscosity.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 10:00 hrs

#### Philipp Grete (Goettingen)

Large eddy simulations (LES) are a powerful method to reduce the billions degrees-of-freedom in numerical simulations of astrophysical magneto-hydrodynamical (MHD) turbulence to a tractable number. This is achieved by simulating only the largest scales directly and employing a subgrid-scale model for the smallest scales. Formally this procedure introduces new, unclosed terms in the MHD equations which encode the interaction of small-scale unresolved motion with both the small and large scales. In this talk we present a new nonlinear model which is systematically tested along with a set of traditional models. We find that the new nonlinear model outperforms the traditional ones in all tests conducted including the representation of the energy flux along the turbulent cascade.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Sara Saracino (University of Bologna)

By exploiting the exceptional high-resolution capabilities of the near-IR camera GSAOI combined with the multi-conjugate adaptive optics system GeMS at the 8.1 m GEMINI South Telescope, we are carrying on a project aimed at probing the nature of a selected sample of globular clusters in the Galactic bulge. In this talk I will present the promising results obtained for Liller 1, an heavily obscured cluster and NGC 6624. We realized the deepest and most accurate near-IR color-magnitude diagram (CMD) ever obtained for Liller 1. We used these data to build new star density and surface brightness profiles for the cluster, and to re-determine its main structural parameters (center of gravity, scale radii, concentration parameter, etc). We found that Liller 1 is significantly less concentrated and less extended than previously thought. Still it has one of the largest collision rates (the second after Terzan 5) among all star clusters in the Galaxy, thus confirming that it is an ideal environment for the formation of collisional exotic objects (such as millisecond pulsars). NGC 6624 is an ideal target to assess the capabilities of GSAOI + GeMS. By using only these images we obtained the deepest CMD of a crowded field ever obtained from the ground, spanning a range of about 10 magnitudes from the horizontal branch level to the second main sequence knee. Finally, the photometry of NGC 6624 was also accurate enough to estimate its age: 12.0 +/- 0.5 Gyr.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Mónica Rubio (Universidad de Chile)

In the standard paradigm stars form out of molecular clouds. These clouds are dense concentrations of H2 that are traditionally traced in external galaxies using transitions of CO or other, more complex, molecules. But dwarf irregular (dIm) galaxies seemingly contradict this fundamental picture. Tracers of recent star formation, such as H-alpha or far-ultraviolet (FUV) emission, show that most dwarfs contain young stars and star clusters, but CO observations often yield only upper limits. The supposition is that H2 is actually present in star-forming regions in dIm galaxies even when CO is undetected. The structure of star-forming clouds at low metallicity is predicted to be different from that at high metallicity. As the metallicity drops, the cold and dense, CO-emitting part of a cloud where stars form shrinks relative to the warm photo-dissociation region (PDR) around it. The molecular hydrogen part can become much more extensive than the CO, and the atomic hydrogen layer around all of this can be more extensive still. I will present the results of the properties of the molecular clouds in low metallicity galaxies along the sequence of decreasing metallicity from the LMC (50% solar), the SMC (20% solar), and WLM (13% solar). CO observations with ALMA of star-forming regions at the lowest metallicities of these dwarfs, shows, in the case of the WLM galaxy, tiny CO clouds inside much larger molecular and atomic hydrogen envelopes.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Eduardo Bañados (Max Planck Institute for Astronomy)

High-redshift quasars provide unique information about the evolution of supermassive black holes, their host galaxies, and the intergalactic medium at early cosmic time. Numerous studies have established a sample of ~60 quasars at 5.5 that the end of cosmic reionization occurred at z~6. These findings suggest that fundamental changes are happening in the intergalactic medium at 6 spans a factor of ~20 in luminosity and shows a diverse range of properties, including a number of weak-line and radio-loud quasars. I will also discuss some of the surprises revealed by this quasar sample as well as our initial follow up studies, which are the first steps towards a statistical characterization of the high-redshift quasar population.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Pierre Cox (ALMA)

The Atacama Large Millimeter/submillimeter Array (ALMA) is an aperture synthesis interferometer that currently operates from wavelengths of 3 mm to 350 microns with up to sixty six (66) array elements, fifty four (54) of 12-m diameter and twelve (12) of 7-m diameter. The array is located at the ALMA Array Operations Site (AOS) on the Chajnator plateau (at an altitude of about 5000 meters) in the Atacama desert in northern Chile. While the antennas and most of the hardware for the receivers are on site, array capabilities are still expanding and the observatory is ramping up towards full operations. Early science observations have been ongoing since October 2011 and ALMA will soon start the fourth cycle of Early Science observations. Many exciting, fundamental results have already been obtained. I will review the current status of the project, the array performance, testing, and development projects and present a selection of some of the most exciting scientific results from the solar system to the early universe. In short, I will present ALMA: past, present and future

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 17:00 hrs

#### Sebastian Kamann (University of Göttingen)

Past research has revealed many intriguing aspects about the nature of globular clusters, ranging from the detection of multiple populations to the possibility of intermediate-mass black holes residing in their centres. Still, our understanding of globular clusters is limited by the challenges of performing spectroscopy in crowded stellar fields. A striking example is the search for intermediate-mass black holes, where different studies came to conflicting results. However, new instruments for performing spatially resolved spectroscopy in combination with sophisticated analysis techniques promise to overcome these limitations.

In my talk, I will present the first results from a survey of Galactic globular clusters with the panoramic integral field spectrograph MUSE. It aims at obtaining spectra for more than 10000 stars in the central region of each cluster and facilitates a wide range of scientific applications, such as the study of multiple populations, the distribution of binary periods, and the search for black holes.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 14:00 hrs

#### Walter Max-Moerbeck (National Radio Astronomy Observatory, Socorro, NM, USA)

Blazars are a class of active galactic nuclei with jets pointing very close to the observer’s line of sight. The small angle of the jet and the propagation of energetic disturbances at relativistic speeds result in compact and variable emission from radio to gamma-ray energies, that can be used to investigate the nature of these objects. Although much has been learned about jets in active galaxies, there are still many open questions regarding the precise location of the gamma-ray emission site and the details of the mechanism launching the jets. I will show how observations from the OVRO 40 meter telescope blazar monitoring program and the Fermi Gamma-ray Space Telescope are used to understand the relation between the radio and gamma-ray emission sites, thus helping us locate the origin of the gamma-ray emission in blazars. I will also briefly describe a project that explore the emission mechanism and magnetic field structure in parsec scale jets using the Very Long Baseline Array in a blazar that shows quasi-periodic variability in the radio band. These investigations demonstrate the importance of milli-arcsecond resolution observations along with multi-wavelength monitoring as tools to study the jets of active galaxies, and the promising prospects for future discoveries when new telescopes like LSST and CTA begin to operate and are used in combination with existing facilities.

Lugar: Our Auditorium (first floor, new astro-building)

Hora: 16:00 hrs

#### Michel Curé (Universidad de Valparaíso)

he measurement of the equatorial rotational speed (v) of a star is not direct, instead what is measured is the product v sin(i), where is is the inclination angle between the rotational axis and the line of sight. Once we have a sample of “v sin(i)” under the assumption that rotational axes are distributed uniformly over the unitary sphere we enhanced the pioneer work of Chandrasekhar and Muench (1950) and obtained in close form the solution of the cumulative distribution function (CDF) of the rotational speeds. Then, we show that for stellar cluster this assumption of uniformity seems to be wrong when the members interact gravitationally. Finally we propose a new model to describe the distribution of axes.

Lugar: Auditorium (first floor)

Hora: 11:00 hrs

#### Maxim Dvornikov (University of Sao Paulo, Brazil; Institute of Terrestrial Magnetism…

Magnetars are neutron stars having extremely strong magnetic fields B > 10^15 G. Despite the existence of numerous models for the generation of such magnetic fields, the issue of the origin of magnetic fields in magnetars still remains open. We propose the new model for the generation of strong magnetic fields in magnetars based on the magnetic field instability in matter composed of electrons and nucleons interacting by the parity violating electroweak forces.

I start with the brief description of general properties of neutron stars and magnetars. Then I review some previous models for the generation of magnetic fields in magnetars. I also discuss the main physics ingredients of our model, which include the chiral magnetic effect, the Chern-Simons theory in presence of the electroweak interaction, and the magnetic helicity. Then I obtain the set of kinetic equations, which are used to describe the generation of magnetic fields in magnetars.

In frames of our model, we can predict the growth of a seed magnetic field B_0 = 10^12 G, typical in a pulsar, up to the values observed in magnetars. Magnetic fields generated are of large scale comparable with the magnetar radius. The time of the magnetic field growth is 10^3 – 10^5 yr which is comparable with the ages of young magnetars. Within our approach we also predict the generation of the maximal helicity from initially nonhelical fields. The obtained results are compared with the predictions of other models.

Lugar: Auditorium (first floor)

Hora: 15:30 hrs

#### Sabrina Stierwalt (University of Virginia)

I will present the initial results from TiNy Titans, the first systematic study a sample of interacting dwarf galaxies and the mechanisms governing their star formation. Mergers of massive galaxies provide a significant mode of galaxy evolution and are observed to inspire intense starbursts and significant rearranging of the galaxies’ gas and dust. However, despite the fact that mergers among low mass galaxies outnumber those between massive ones, whether these effects occur in the shallower gravitational potential wells of dwarf galaxies remains completely unconstrained. A few intriguing examples of dwarf-dwarf interactions exist in the literature, but the efficiency of gas removal and the enhancement of star formation in dwarfs via pre-processing (i.e. dwarf-dwarf interactions occurring before the accretion by a massive host) has never been studied for a uniform sample of dwarfs. Our multiwavelength approach gathers high resolution optical, UV, and radio imaging to probe the effects of interactions on the star formation and ISM in a complete sample of dwarf pairs selected from the Sloan Digital Sky Survey. We find star formation is enhanced in paired dwarfs over isolated dwarfs to an even greater extent than is observed in massive galaxies, but the dwarfs involved in interactions still have large gas reservoirs (and thus capacity for future star formation). Our interacting dwarfs tend to be low metallicity and thus offer a unique window into modes of star formation that were important at earlier epochs.

Lugar: Auditorium (first floor)

Hora: 16:00 hrs

#### Dr. Pierre Kervella (Paris-Meudon, UMI francesa-chilena)

The long-period Cepheid RS Pup is one of the most luminous Cepheids in the Milky Way (P = 41.4 days). It is surrounded by a large circumstellar dusty nebula reflecting the light from the central star. The origin and physical properties of the nebula are however uncertain: was it created through mass loss from the star, or is it a pre-existing interstellar cloud ? To address this question, we used the VLT/FORS instrument to map the degree of linear polarization pL in the nebula. Using a simple polarization model, the scattering angle can be recovered from pL, and therefore give access to the 3D dust distribution. We derive a total dust mass of M(dust) = 2.9 +/- 0.9 Msun within 1.8′ of the Cepheid. This very high mass excludes that it was created by the star itself.
Due to the changing luminosity of the central source, spectacular light echoes propagate into the nebula. This remarkable phenomenon can yield a reliable geometric distance to RS Pup, provided we achieve a sufficient accuracy on the 3D structure of the dust distribution. Such a distance is highly valuable e.g. to calibrate the Leavitt law, as well as the Cepheid’s projection factor p used in Baade-Wesselink distance estimates. We obtained 7 epochs of polarimetric imaging with HST/ACS, from which we derive a distance d = 1940 +/- 80 kpc. We are currently evaluating the value of the p-factor for this star, that appears to be close to p = 1.3.

Lugar: Auditorium (first floor)

Hora: 15:30 hrs

#### Anita Zanella (Service d’Astrophysique – CEA Saclay, France)

Giant star forming clumps are typical morphological features of z ~ 2 galaxies, likely formed by violent gravitational instabilities in highly turbolent, gas-rich galaxy disks. However, their formation phase has never been observed. Furthermore, their fate is still highly debated: it is not understood yet if they migrate inward and coalesce to form the galaxy bulge or if they are disrupted by stellar feedback.
With a data set of ultra deep HST/WFC3 imaging and slitless spectroscopy, we selected a sample of 68 [OIII] emitters at z ~ 2. From spatially resolved [OIII], Hb and [OII] emission line maps we serendipitously discovered a bright, off-nuclear, unresolved emission arising in the disk of a galaxy at z = 2. Despite its high contribution to the total star formation rate (SFR) of the galaxy (~ 40%), this feature is not detected in the continuum. We are thus observing, for the first time, a newly formed clump, in the very early phase of its collapse (age < 10 Myr). With a specific SFR 30 times higher than the one of the whole galaxy, this clump is behaving like a galactic miniatu1re of starburst, showing that violent disk instability can induce high efficient star formation. This result is also supported by in-house simulations showing that clumps form with an initial burst with highly enhanced SFR…

Lugar: Auditorium (first floor)

Hora: 16:00 hrs

#### Francesco Valentino (Service d’Astrophysique – CEA Saclay, France)

The most distant spectroscopically confirmed cluster known to date, CL J1449+0856 at z=2, represents a unique laboratory to study galaxy evolution in dense environments at high redshifts and, in the past few years, a systematic multiwavelength campaign allowed us to test the current understanding of environment-driven processes in galaxies.

Surprisingly, recent Subaru and HST spectroscopic follow-ups revealed lower metallicities and higher sSFRs in cluster star-forming galaxies than in mass-matched field counterparts. This somewhat unexpected behaviour can be possibly due to an enhanced accretion of pristine gas from the environment and/or facilitated by recent or ongoing merging activity, something probably linked to the recent assembly of its dark matter halo. The further discovery of a giant Lya halo residing in the cluster core in a narrow-band imaging follow-up and the presence of very strong diffuse light in the near-IR support the idea of a physical connection between Mpc-scale environment and galaxy evolution at the peak of cosmic star formation history at z~2.

Lugar: Auditorium (first floor)

Hora: 16:00 hrs

#### Dr. Raúl Monsalve (Arizona State University)

A key objective in cosmology consists of characterizing the evolution of the universe after the release of the cosmic microwave background (CMB). As predicted by theory, one way of tracking the formation of the first generations of compact objects in the range 40 > z > 6 would be through observations of the 21-cm line emitted by neutral atomic hydrogen (HI) in the intergalactic medium (IGM) due to the hyperfine splitting of its ground state, and now redshifted from 1.4204 GHz down to the VHF range, therefore, its detection is being attempted through interferometric and global (spatially averaged) observations at frequencies between 40 and 200 MHz. The talk will describe the project “Experiment to Detect the Global EoR Signature (EDGES)”, which is currently operating in the desert of Western Australia. This instrument represents the state of the art in global measurements of the 21-cm signal from the epoch of reionization (EoR), corresponding to 15 > z > 6. Finally, it will describe the efforts of a project called MARI-UCSC that attempts to find radio-quiet locations in the Chilean Atacama Desert, which could become sites for conducting competitive low-frequency observations.

Lugar: Auditorium (first floor)

Hora: 11:00 hrs

#### Richard de Grijs (Kavli Institute for Astronomy and Astrophysics, Peking University)

Until about a decade ago, star clusters were considered “simple” stellar populations: all stars in a cluster were thought to have similar ages and the same metallicity. Only the individual stellar masses were thought to vary, in essence conforming to a “universal” initial mass function. Over the past decade, this situation has changed dramatically. Yet, at the same time, star clusters are among the brightest stellar population components and, as such, they are visible out to much greater distances than individual stars, even the brightest, so that understanding the intricacies of star cluster composition and their evolution is imperative for understanding stellar populations and the evolution of galaxies as a whole. I will discuss my group’s recent progress in this context, with particular emphasis on the properties and importance of binary systems, the effects of rapid stellar rotation, and the presence of multiple populations in Local Group star clusters across the full age range. Our very recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate- age (~2 Gyr-old) star clusters, which opens up exciting avenues for future research directions.

Lugar: Auditorium (first floor)

Hora: 16:00 hrs

#### Dr. Raúl Monsalve (Arizona State University)

A key objective in cosmology consists of characterizing the evolution of the universe after the release of the cosmic microwave background (CMB). As predicted by theory, one way of tracking the formation of the first generations of compact objects in the range 40 > z > 6 would be through observations of the 21-cm line emitted by neutral atomic hydrogen (HI) in the intergalactic medium (IGM) due to the hyperfine splitting of its ground state, and now redshifted from 1.4204 GHz down to the VHF range, therefore, its detection is being attempted through interferometric and global (spatially averaged) observations at frequencies between 40 and 200 MHz. The talk will describe the project “Experiment to Detect the Global EoR Signature (EDGES)”, which is currently operating in the desert of Western Australia. This instrument represents the state of the art in global measurements of the 21-cm signal from the epoch of reionization (EoR), corresponding to 15 > z > 6. Finally, it will describe the efforts of a project called MARI-UCSC that attempts to find radio-quiet locations in the Chilean Atacama Desert, which could become sites for conducting competitive low-frequency observations.

Lugar: Auditorium (first floor)

Hora: 11:00 hrs

#### Cristian Saez (University of Maryland)

Originally discovered by Steidel et al. (1998), the SSA22 protocluster lies at z = 3.09 and contains several powerful active galactic nuclei, numerous Lyman-break galaxies (LBGs) and Lyman-α emitters (LAEs), and multiple spatially extended Lyman-α blobs. The protocluster has been mapped using the LAE population, which has revealed a belt-like structure across a 60×20 Mpc^2 (comoving size) region. Cosmological models predict that the protocluster would have collapsed into a z = 0 estructure resembling a rich local cluster (e.g., Coma). In this talk I will describe my latest work on the SSA22 protocluster field though VLT VIMOS, Keck DEIMOS and Keck LRIS multi-object spectra of 366 sources in the field of the z ≈ 3.09 protocluster SSA22. Sources are spectroscopically classified via template matching, allowing new identifications for 206 extragalactic sources, including 37 z > 2 LBGs and LAEs, 8 new protocluster members, and 94 X-ray sources from the ∼ 400 ks Chandra deep survey of SSA22

Lugar: Auditorium (first floor).

Hora: 17:00 hrs

#### Loreto Barcos-Muñoz (University of Virginia)

Many of the most luminous galaxies in the local universe are distant, compact, heavily dust-embedded merger-induced starbursts – properties that make them difficult to study in detail. Radio continuum produced by star formation and/or AGN activity offers a way to peer past the dust of these galaxies and still achieve very high spatial resolutions. My PhD. thesis mainly focuses on the study of new, high-resolution, multi-frequency (4-8 GHz and 29-36 GHz) radio continuum maps obtained with the recently upgraded Karl G. Jansky Very Large Array of 22 local luminous and ultraluminous infrared galaxies. The high resolution at 33 GHz (< 0.1″ ~ 50 pc at 100 Mpc) and sensitivity to all spatial scales allows us to make the best measurements to date of the true size of the any nuclear starburst, and to determine the spectral energy distribution of the bright cores of these galaxies, which will allow us to constrain the nature of the central energy source

Lugar: Auditorium (first floor)

Hora: 11:00 hrs

#### Ulrike Kuchner (Department for Astrophysics, University of Vienna)

Galaxy evolution implies the process of both rapid and gradual) change occuring in galactic systems and we see much evidence for this over the course of cosmic history. With modern instrumentation we can study dense regions in the cosmic web building up in time and the galaxies within changing their properties: We analyze galaxies in the field of very massive clusters, utilizing deep high- resolution HST imaging from the HST Treasury program CLASH Postman et al. 2012), complemented by Subaru BVRIz imaging which maps the large scale environment of the clusters to measure internal stellar structures, sizes and masses. Exploiting CLASH-VLT VIMOS spectra over the whole area of 30×30 sq.arcmin, we additionally gain accurate star-formation rates and oxygen abundances gas metallicities)…

Lugar: LF207 (Ground floor)

Hora: 15:00 hrs

#### Laura Pérez (NRAO)

The growth of dust inside circumstellar disks is a fundamental component of the planet formation process. In the current planet formation scenario the smallest grains easily grow to larger sizes, but once macroscopic sizes are attained difficulty arises: not only collisional coagulation efficiencies drop, but the interaction of grains with the gaseous disk contributes to their demise by radial drift. Radio-wave observations — from sub-mm to cm wavelengths — directly trace the emission from dust of different sizes, allowing us to study their growth from micron-sized dust grains to centimeter-sized particles. I will discuss recent observational constraints of particle growth in protoplanetary disks, which are only now possible thanks to sensitive observations with radio-interferometers, particularly at cm-wavelengths with the VLA. In the systems studied, larger particles were segregated to the inner disk regions, consistent with theoretical models of grain growth and transport. This new observational evidence provides support to radial drift being a barrier for further growth into larger solids. A possible solution to this problem exist: regions of local pressure maxima that can efficiently trap grains and create appropriate conditions for growth. I will present recent ALMA observations that reveal large-scale asymmetries in the disk dust distribution, which may be the observational signature of these regions.

Lugar: Auditorium (first floor)

Hora: 11:00 hrs

#### Francisco Förster Burón (Center for Mathematical Modeling, CMM)

At the Astroinformatics Laboratory of the Center for Mathematical Modelling (CMM) at the University of Chile and the Millennium Institute for Astronomy (MAS) we have developed a novel transient detection pipeline to be used in real-time with data from the Dark Energy Camera (DECam). DECam is a 520 Megapixel CCD camera with an unprecedented wide angle field of view mounted on the 4m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO). During five contiguous nights in the first week of March of 2014 we were able to achieve the real-time data analysis of more than 120 square degrees of the sky with a cadence of only two hours and a processing time of less than one exposure time for every image. We processed more than 400 billion pixels in total, leading to the discovery of 12 newly exploding SNe in almost real-time. We found thousands of previously unknown asteroids and hundreds of variable stars that can be used to map the structure of the outer parts of the Milky Way.

Lugar: Auditorium (first floor)

Hora: 15:00 hrs

#### Jacob Kooi (CalTech/JPL)

The Large Latin American Millimeter Array (LLAMA) is a joint project of Argentina and Brazil aimed at installation, operation, and maintenance of a 12m‐diameter antenna in the northwestern part of Argentina to explore the southern sky.
Among the goals of this endeavor: i) to enables Brazilian and Argentinean astronomers to gain access, and participate in ALMA, ii) single dish spectroscopic and continuum observations, iii) to participate in EHT/VLBI with others instruments such as ALMA, APEX, ASTE, etc. iv) mm and sub-mm continuum and astronomical line studies from the solar neighborhood to high redshifted galaxies, v) extended surveys with intermediate angular resolution (30 o South).

Lugar: Auditorium (first floor)

Hora: 14:00 hrs

#### George C. Privon (UdeC)

Luminous Infrared Galaxies (LIRGs; 10^11 < L_IR [8–1000 um]/L_sun < 10^12) and Ultraluminous Infrared Galaxies (ULIRGS; L_IR/Lsun > 10^12) are the most extreme star forming systems in the local universe, in terms of their absolute star formation rates—tens to hundreds of times that of “normal” galaxies—as well as their star formation rate densities. Additionally, many U/LIRGs host active galactic nuclei, making these systems ideal for studying the co-evolution of galaxies and their supermassive black holes. The activity in U/LIRGs is generally driven by galaxy interactions and mergers, so the star formation and AGN maybe occurring as these systems undergo a morphological transformation from disk to spheroidal systems. I will discuss recent and ongoing work to combine multi-wavelength observations with matched numerical simulations of local U/LIRG mergers. Specifically, I will describe early results from a program of matching N-body simulations to individual U/LIRG mergers. I will also highlight results from two surveys of the molecular and neutral atomic ISM in local U/LIRGs. Finally, I will conclude with a brief summary of my plans for the next several years.

Lugar: Auditorium (first floor)

Hora: 17:00 hrs

#### Bryan Miller (Gemini Observatory)

I will present recent work to study the globular clusters and nuclei in dwarf elliptical galaxies in the Virgo and Fornax Clusters. Gemini/GMOS spectroscopy shows that the globular clusters are mostly old and metal-poor, very similar to the globular clusters in the Milky Way halo. The nuclei tend to be more metal-rich than the globular clusters. The [alpha/Fe] ratio appears to be solar for the globulars, but the nuclei may be slightly alpha-enhanced. We also use the kinematics of the globular clusters to estimate the masses and mass-to-light ratios of the dwarfs. The dwarfs in our sample have masses around 10^10 Msun and are not strongly dark matter dominated. We also see differences in globular cluster specific frequencies between different types of dwarf galaxies. Implications of these results on dwarf elliptical galaxy formation and evolution will be discussed.

Luminous Infrared Galaxies (LIRGs; 10^11 < L_IR [8–1000 um]/L_sun < 10^12) and Ultraluminous Infrared Galaxies (ULIRGS; L_IR/Lsun > 10^12) are the most extreme star forming systems in the local universe, in terms of their absolute star formation rates—tens to hundreds of times that of “normal” galaxies—as well as their star formation rate densities. Additionally, many U/LIRGs host active galactic nuclei, making these systems ideal for studying the co-evolution of galaxies and their supermassive black holes. The activity in U/LIRGs is generally driven by galaxy interactions and mergers, so the star formation and AGN maybe occurring as these systems undergo a morphological transformation from disk to spheroidal systems. I will discuss recent and ongoing work to combine multi-wavelength observations with matched numerical simulations of local U/LIRG mergers. Specifically, I will describe early results from a program of matching N-body simulations to individual U/LIRG mergers. I will also highlight results from two surveys of the molecular and neutral atomic ISM in local U/LIRGs. Finally, I will conclude with a brief summary of my plans for the next several years.

Lugar: Auditorium (first floor)

Hora: 17:00 hrs

#### Christopher Paul Haines (U Chile)

I present an analysis of star formation among galaxies in and around 30 massive clusters at z=0.15-0.30, combining Spitzer 24um and GALEX NUV imaging from the Local Cluster Substructure Survey (LoCuSS) with extensive spectroscopy from the Arizona Cluster Redshift Survey, including >10,000 confirmed cluster members.
I will present a series of results that demonstrate that most (if not all) massive star-forming galaxies accreted into clusters must have their star formation slowly quenched on 1-2 Gyr time-scales. To understand how the observed trends relate to the continual accretion of star-forming spirals onto massive clusters and subsequent quenching of star-formation, I follow the infall and orbits of galaxies in the vicinity of 75 massive clusters extracted from the Millennium cosmological simulation, obtaining a series of predicted model trends that have general applicability for understanding galaxy evolution in cluster environments. I also present results demonstrating the need for pre-processing in groups, consistent with the an over-abundance of X-ray groups in the outskirts of our cluster sample.

Lugar: Auditorium (first floor)

Hora: 16:00 hrs

#### Mario Soto

I will report on two ongoing projects currently being carried out at the Space Telescope Science Institute (STScI). The first project studies the proper motions in several low foreground extinction windows of the Galactic bulge in 10 fields strategically placed on both ends of the Galactic bar and the Galactic minor-axis. The second project attempts to characterize the multiple stellar populations patterns in a sample of 55 globular clusters by observing them in the UV/blue WFC3 UVIS filters F275W, F336W, and F438W. A detailed account of both project motivations and techniques will be presented, as well as their respective current status, including new results.

Lugar: Auditorium (first floor)

Hora: 11:00 hrs

#### Claudia Cicone

Understanding the negative feedback mechanisms responsible for regulating and quenching star formation in galaxies, represents a crucial step in solving some of the major open problems in galaxy formation and evolutionary models. In particular, “quasar-mode” negative feedback is often invoked by these models to prevent massive galaxies from overgrowing and to account for the ”red-and-dead” properties of massive local and high redshift (z ~ 2) galaxies. The recent discovery of powerful and large-scale outflows of molecular gas in several local (U)LIRGs constitutes a major breakthrough in this field.

I will present our latest study (Cicone et al. 2014) in which we exploit CO(1-0) interferometric observations to make a significant step forward in understanding the properties of massive molecular outflows, their connection with the central AGN and with the ongoing starburst and their profound feedback on the host galaxy. I will also show new exciting results on the quasar-feedback mechanisms in action in the very early Universe, presenting recent interferometric follow-up observations of the extremely massive and extended quasar-driven outflow detected in a quasar-host HyLIRG at redshift z=6.4 using the [CII]158 $\mu$m emission line (Maiolino et al. 2012, Cicone et al. in prep).d

Lugar: Auditorium (first floor)

Hora: 17:00 hrs

#### Graeme Candlish

The study of black hole solutions to Einstein’s field equations of General Relativity (GR) has been a major area of research in theoretical physics. In recent years there has been increased interest in the study of solutions in more than four spacetime dimensions. In this talk I will give a brief summary of various black hole solutions in GR, in both four and five dimensional spacetimes. I will then discuss in more detail solutions describing multiple (electromagnetically charged) black holes and the results of studies of their smoothness properties.

Lugar: Auditorium (first floor)

#### Blesson Mathew

In this talk, I will be presenting our recent published work of two Be stars in the 70-80 Myr old open cluster NGC 6834. NGC 6834(1) has been reported as a binary from speckle interferometric studies whereas NGC 6834(2) may possibly be a gamma Cas-like variable. Infrared photometry and spectroscopy from UKIRT, and optical data from various facilities are combined with archival data to understand the nature of these candidates. I will also be discussing another work in progress, which is the mid-infrared studies of Be stars using the photometric data from WISE mission. We have got some interesting results, which question the conventional wisdom of free-free emission being responsible for IR excess in Be stars. Also, I would like to share some studies on Herbig Be stars, which shows similarity with classical Be stars, in spectral features.

Lugar: Auditorium (first floor)

#### Pau Amaro-Seoane

One of the most interesting sources of gravitational waves is the inspiral of compact objects on to a massive black hole (MBH), commonly referred to as an extreme-mass ratio inspiral. The small object, typically a stellar black hole, emits significant amounts of GW along each orbit in the detector bandwidth. On the other hand, recent observations of the Galactic center revealed a dearth of giant stars inside the inner parsec relative to the numbers theoretically expected for a fully relaxed stellar cusp. The possibility of unrelaxed nuclei (or, equivalently, with no or only a very shallow cusp) adds substantial uncertainty to the estimates. I show that under quite generic initial conditions, the time required for the growth of a relaxed, mass segregated stellar cusp is shorter than a Hubble time for MBHs with masses <~ 5 x 10^6 Msun and connect this fact to the missing stars in the RGB via formation of a disk at the Galactic Center. After the star-forming episode, I prove that that disk is responsible for the thermalization of eccentricities of the S-stars and the absence of Wolf-Rayet (WR) and O-stars inside 1″.

Lugar: Auditorium (first floor)

#### Lorenzo Monaco

The study of the light element lithium offers clues to the understanding of different problems in astrophysics, ranging from cosmology to the stellar evolution theory. I will present:

(i) the results of the spectroscopic investigation on the lithium content among unevolved stars in globular clusters. GCs are among the the oldest objects in the Universe and the study of their lithium content may provide insights into the physical conditions during the big bang nucleosynthesis (BBN) phase. In particular, they can help understand the so called “cosmological lithium problem”, i.e. the discrepancy between the constant lithium abundance measured in warm metal poor halo stars and the prediction of the standard BBN theory coupled with the the baryonic density measured by WMAP/Planck satellates. They can also provide hints to the origin of the multiple stellar populations in GCs. I will also present:

(ii) the results of a search for Li-rich giants among thick disk stars and in open clusters. An overall dilution of the surface stellar lithium content happens as soon as a star evolve off the main sequence. Nevertheless, a few percent of giant stars present high lithium abundances, whose origin is not yet completely understood, particularly for low mass stars.

Lugar: Auditorium (first floor)

#### Chris Lidman

Covering the 50 square degrees of Spitzer SWIRE Legacy Fields, the Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is one of the largest surveys of its kind. It has detected hundreds of galaxy clusters up to z=1.7. Over the past few years, the SpARCS team has been examining the properties of galaxies in these clusters though multi-wavelength imaging and multi-object spectroscopy. In this talk, I will discuss what we are learning about galaxy evolution in these the densest of environments. I will also discuss our plans to push these studies to even higher redshifts where it seems that drastic changes to the galaxy population in the cores of clusters is occurring.

Lugar: Auditorium (first floor)

#### Richard Lane

Since starting my first postdoc three years ago at Astro-UdeC I have been working on various topics, including Galactic globular clusters, the Sagittarius dwarf galaxy, collisional ring galaxies, Galactic evolution, and isolated elliptical galaxies. To make this an interesting talk for as many people as possible, I will cover some of my favourite topics, including my most recent work on Galactic globular clusters and isolated elliptical galaxies, with some smatterings of the Sagittarius dwarf thrown in for good measure.

Lugar: Auditorium (first floor)

#### Cristina Romero Cañizales

The so called luminous infrared galaxies (10^11 L_sun < L_IR < 1012 L_sun), LIRGs, dominate the IR background and the star formation rate (SFR) density at z~1. The boost of massive star formation in LIRGs can be inferred from the presence of core-collapse supernovae (CCSNe), which can be uniquely studied at radio frequencies (where light is unaffected by dust extinction). Furthermore, CCSN counts represent a great aid to measure the SFR in such highly obscured systems. In this talk I will present the case of the LIRG Arp299.

Lugar: Auditorium (first floor)

Hora: 14:00 hrs

#### Rebecca Davies

We use the Wide-Field Spectrograph (WiFeS) on the ANU 2.3m telescope to investigate the power sources of the composite activity in the luminous infrared galaxy NGC7130. We show that NGC7130 is a spectacularly clean case of starburst + AGN activity. We observe clear and distinct rings of gas ionised by increasing fractions of AGN activity towards the nucleus. We use our data to robustly estimate the relative contribution of star-formation and AGN activity to the EUV radiation field in NGC7130, and our integral field data allows us to estimate the radius of the narrow line region. This analysis paves the way for a large investigation into the power mechanisms responsible for the composite optical class of galaxies.

Lugar: Auditorium (first floor)

#### Peter Pessev

In this presentation I will outline three recent research projects focused on star clusters from the Milky Way to distant galaxies in the field. These projects reflect areas of personal research interest and represent small building blocks of the great puzzle of star and structure formation in the Universe. More specifically I am going to talk about (in order of increasing distance):

Element abundances in highly the obscured Galactic Globular Clusters Mercer 5 and 2MASS-GC02 Evidence of variable IMF from observations of Galactic and Magellanic Cloud star clusters Extragalactic Globular Cluster Systems of Isolated Galaxies

Lugar: Auditorium (first floor)

#### Peter Pessev

The Gemini South Adaptive Optics Imager (GSAOI) is the imaging camera to be used with the Multi-Conjugate Adaptive Optics system (GeMS) at Gemini South. GeMS and GSAOI are capable of delivering diffraction limited images in the Near-Infrared (0.9-2.5 micrometer) over an 85″ square field of view. The focal plane of the instrument is covered by 2 x 2 array of HAWAII 2RG detectors and has a plate scale of 0.02″. The instrument optics are all-refractive and coupled with the superb spatial resolution, taking full advantage of the unprecedented image quality delivered by GeMS. GSAOI went through commissioning at Gemini during the 2011/2012 period followed by SV and the first semester of regular science operations. In this presentation, I will give an outline of the system, its performance, and briefly summarize some early science results.

Lugar: Auditorium (first floor)

Hora: 14:00 hrs

#### Geronimo Villanueva

A pesar de la incesante expansión del Universo iniciada con el Big Bang 14 mil millones de años atrás, nuestro Universo se siente cada día más cercano. La inquebrantable vocación de la humanidad por descubrir nuevos horizontes ha permitido el acercamiento de civilizaciones en nuestro planeta y nos ha permitido conocer nuestro lugar en el Universo como nunca antes. Desde la Ilustración a la actualidad, la explosión de conocimiento nos ha llevado a la Luna, pronto a Marte y luego a inimaginables horizontes. Vivimos en una época única, en donde la exploración de nuestro Sistema Solar no es un sueño, sino una tangible y estimulante realidad. En la División de Exploración del Sistema Solar de NASA, estamos investigando los posibles destinos de nuestros próximos viajes espaciales (robobitos y tripulados) como también los lejanos e intrigantes planetas extrasolares. Recientemente con nuestro descubrimiento de metano en la atmósfera de Marte, la exploración del planeta rojo ha tomado un gran impetu. Metano es un indicador de biología en nuestro planeta, siendo que este es producido en más de un 90% por actividades antropogénicas y biológicas.

En esta reunión, presentaré recientes resultados de nuestra búsqueda de indicadores biológicos en Marte utlizando espectroscopia de alta resolución con el Very Large Telescope (VLT) en Cerro Paranal (Chile), y los telescopios Keck II y NASA-IRTF en Hawaii; como también el futuro de la exploración espacial proyectado por NASA y la Agencia Espacial Europea (ESA).

Lugar: Auditorium (first floor)

#### Bodo Ziegle

Our general view of galaxy evolution with a peak of cosmic star formation and the establishment of morphologies about 8-10 Gyrs ago needs a physical fundament for the driving forces and acting processes. I’ll present a selection of studies we perform in Vienna to initiate future collaborations with Concepcion. The local IFU survey CALIFA reveals details of physical properties like ionization mechanisms and angular momenta. Kinematic features reveal interaction mechanisms also at larger lookback times and we trace the evolution of the Tully Fisher relation out to z=1. In between, we use CLASH clusters to probe environmental effects on galaxy properties. At the peak epoch of cSF, we measure abundances of the warm ionized gas in zCOSMOS while at redshifts approaching re-ionization we examine the cold molecular gas and dust of sub-mm galaxies.

Lugar: Auditorium (first floor)

#### Kevin Schawinski

Massive galaxies are broadly split into those forming stars on the main sequence, and those which are quiescent. The physical processes by which galaxies quench their star formation remain poorly understood. I analyze the properties of galaxies and track their evolutionary trajectories as they migrate from the blue cloud of star forming galaxies to the red sequence of quiescent galaxies via the green valley’. I show that there must be two fundamentally star formation quenching pathways associated with early- and late-type galaxies and discuss potential physical mechanisms, including environment and black hole feedback.

Lugar: Auditorium (first floor)

#### Joerg Dabringhausen

Ultra-compact dwarf galaxies (UCDs) are stellar systems with masses similar to those of dwarf elliptical galaxies (dEs), but with characteristic radii that are about a factor of ten smaller than those of dEs. One of the most intriguing properties of UCDs is that the mass-to-light ratios implied by their internal dynamics are rather high, even though it is unlikely that UCDs contain significant amounts of dark matter. This suggests that the reason for the high mass-to-light ratios is a varying stellar initial mass function (IMF) in UCDs, even though the IMF seems remarkably invariant in the Milky Way. This apparently invariant IMF for star forming systems in the Milky Way is known as the canonical IMF. In principle, the mass-to-light ratios of an old stellar population be increased either by additional faint, low-mass stars or by additional remnants of massive stars. In order to decide which one of these two cases applies to the UCDs, the frequency of bright X-ray sources in UCDs was studied. This is because a bright X-ray source in a UCD can be interpreted as a low-mass X-ray binary (LMXB), which is composed of a low-mass star and a stellar remnant. The fraction of the UCDs in the Virgo cluster that also contain a bright X-ray sources is indeed remarkably high, and the variation of the IMF that explains the overabundance of LMXBs in these UCDs is consistent with their high mass-to-light ratios. This suggests that the UCDs formed with a larger number of massive stars than the canonical IMF would imply. As a consequence, the UCDs would have been extremely dense when star-formation took place in them. These extreme initial conditions may be the reason why the IMF in UCDs would deviate from the canonical IMF in the first place. Regarding the origin of the UCDs, it has been argued before that they are created by the interaction between gas-rich galaxies. However, the formation of dEs may have been triggered by the same process, even though their structural parameters are largely different from those of UCDs. This notion is supported (among other reasons) by the finding that young galaxies that formed through the interaction between gas-rich galaxies would evolve naturally into dEs as far as their masses and radii are concerned. This formation scenario for dEs poses however a challenge to the currently prevailing cosmological model.

Lugar: Auditorium (first floor)

#### Nikolay Kacharov

NGC 4372 is a poorly studied, old, and very metal poor Globular Cluster (GC) located close to the Galactic disk and suffering from a severe differential reddening. It was likely dynamically stirred during its frequent crossings of the Galactic disk.

Here, I will present the first ever high-resolution observations of it, taken with the FLAMES instrument at the VLT. Our sample consists of 131 unique red giant stars, confirmed cluster members. We found [Fe/H] = -2.2 ± 0.1 dex without any significant metallicity spread. We have also derived the abundances of several alpha, iron-peak and n-capture elements, as well as the p-capture element Sodium, which is crucial to assess the existence of multiple populations in this GC.

I will focus on the kinematic properties of NGC 4372. Based on precise radial velocities and an analytic Plummer model, we have computed the central velocity dispersion sigma0 = 4.7 ± 0.9 km/s and we also found a clear signal of systemic rotation with an amplitude v_rot = 2.0 ± 0.2 km/s. NGC 4372 has unusually high systemic rotation to velocity dispersion ratio for its metallicity, which puts it in line with other very metal poor GCs like M 15 and NGC 4590, and could bring some clues to the origin of those very low metallicity systems. Finally, we found a mild flattening of NGC 4372 in the direction of its rotation. This observation favours that the flattening is indeed caused by the systemic rotation rather than tidal interactions with the Galaxy.

Lugar: Auditorium (first floor)

#### Mike Brotherton

Large galaxies harbor supermassive black holes in their centers, and correlations between the mass of those black holes and the properties of their hosts indicate closely tied evolutionary histories. Black holes grow when rapidly accreting material and shining as active galaxies, the brightest of which are quasars.

Reverberation mapping provides direct mass measurements of the central black hole of quasars, exploiting the fact that the broad emission lines seem to arise primarily from virialized gas. Scaling relationships based on reverberation mapping results permit mass estimates based on single-epoch spectra, but suffer from large scatter. We are now in the era of first and second-order corrections, accounting for sources of scatter, that can improve these estimates. I demonstrate several of these recent mass improvements based on orientation effects and contamination from non-reverberating emission-line regions, and discuss current work enabled by Chilean observatories that will play a pivotal role in the advancement of this field.

Lugar: Auditorium (first floor)

Nuclei of galaxies usually contain large amounts of dust that absorb the radiation in all the wavelengths but in the millimetre/submillimetre regime. For this reason, molecular emission is often the best tool to study those regions, and the processes associated to the accretion of material onto supermassive black holes, or the formation of stars in powerful starburst events. I will show a few molecular line surveys done toward the centres of starbursts, AGNs and ULIRG galaxies, and explain how the molecular emission can be linked with the physical properties of the gas, such as cosmic rays and X-rays strengths, shocks, or UV fields.

Lugar: Auditorium (first floor)

#### Mia Bovill

The formation and evolution of the smallest dwarfs presents an unique window into external and internal feedback in lowest mass galaxies. The lowest luminosity dSphs provide near field observation tests for star formation during the epochs of the first galaxies and reionization. Using simulations which trace the fate of the first galaxies to z = 0, I will argue that the faintest dwarf satellites of the Milky Way and M31 formed the bulk of their stars before reionization and are the first of these primordial galaxies to be discovered. However, models which reproduce this primordial galaxy population overproduce the number of more massive, bright satellites.

Lugar: Auditorium (first floor)

#### Steve Majewski, University of Virginia, Estados Unidos

Lugar: Auditorium (first floor)

#### Carmela Lardo, Universidad de Bologna, Italia

Using UV images taken with the Telescopio Nazionale Galileo, we discovered an anomalous sequence in the color-magnitude diagram of M2. This narrow, poor-populated red giant branch extends down to the sub giant branch region (SGB), and appears to be linked to the split SGB reported by Piotto et al. We obtained MODS low-resolution spectroscopy of 15 giants in M2, located on the double RGB in V, U − V diagram, with the goal to chemically characterize these two groups of stars. The low-resolution (R~1000), blue spectra were then analyzed via spectrum synthesis technique. The high quality of the data allowed us to measure C, N, Ba and Sr abundances relative to iron for 15 RGB stars distributed along the two sequences. We added to the MODS sample C and N measurements for 35 additional stars belonging to the blue RGB sequence, presented in our previous work. We find a clear separation between the two groups of stars in s-process elements as well as C and N content. Both groups display a C–N anticorrelation and the red RGB stars are on average richer in C and N with respect to the blue RGB. Among the GCs with photometric evidence of multiple populations only NGC 1851 and M 22 display a bimodal SGB which is photometrically connected to the split RGB. All the collected evidence indeed reinforce the suggestion that also M2 belongs to the family of globular clusters with a rather complex star formation history.

Lugar: Auditorium (first floor)

#### Gaspar Galaz, PUC, Chile

In this talk I summarize the most important features of low surface brightness galaxies, in particular those populating the faint end of the galaxy luminosity function, dominate the volume number density of extragalactic objects in the universe and also are the astronomical reservoirs of dark matter. I discuss new discoveries and finish the talk with the possible use of new instruments to boost the research on these objects.

Lugar: Auditorium (first floor)

#### Patricia Arévalo, Santiago, Chile

The central engine of AGN is too small to be observed directly, so all our understanding of these sources has been formed by a combination of spectral and variability analyses. The study of the variability of AGN light curves in different energy bands have allowed us to map the structure of the (very compact) engine. Light echos have been used to locate the X-ray corona, the broad line region and the inner edge of the torus. These results confirm broad predictions of the unification model, measure black hole masses, dynamics and ionization structure of the broad-line region, establish the dust-sublimation nature of the inner limit of the torus and finally the connection of the mysterious X-ray corona to the accretion disc.In this talk I will review the most popular methods that have been used to reach all these results.

Lugar: Auditorium (first floor)

Super-massive black hole binaries form after major galaxy mergers,which often involve large amounts of gas flowing to the centre of the new system. Here we present numerical models of binary black holes surrounded by a massive gaseous disc, and show how their interaction shrinks the binary orbit, while at the same time increases its eccentricity and produces a highly variable accretion rate.

Lugar: Auditorium (first floor)

#### Markus Kissler-Patig, Director del Observatorio Gemini

Intermediate-mass black holes, featuring masses of a few hundred to a few tens of thousands solar masses, have recently attracted quite some interest. They fill the gap between solar mass black holes and super-massive black holes and might be at the origin of the formation of the latter. After a decade of controversy, a few reliable intermediate-mass black holes are now known – they appear to lie on the black hole mass – sigma relation defined for super-massive black holes. Coincidence or physical cause? I will review the recent work of our group on intermediate-mass black holes at the centre of Galactic globular clusters and put them into the context of star cluster formation, nuclear clusters and super-massive black holes.

Lugar: Auditorium (first floor)

#### Sergio Torres-Flores, La Serena, Chile

Nearby compact groups of galaxies are ideal laboratories to study galaxy-galaxy interactions. In this sense, the study of nearby interacting galaxies can help us in the interpretation of high-redshift galaxies, where the interaction events were more common. In this talk, I will present some kinematic results obtained for a sample of about 20 Hickson Compact Group (HCG) of galaxies. Using Fabry-Perot data, we have analysed the kinematic of galaxies in these systems and we have found that HCG galaxies display complex kinematics. Most of the galaxies in these systems present perturbed rotation curves and misalignment between optical and kinematic position angles. In order to determine if the environment can play a role in the analysis of the Tully-Fisher relation, we have analysed the near-infrared, stellar and baryonic Tully-Fisher relation for a sample of HCG galaxies and we compared it with the relations defined by non-interacting galaxies (from the GHASP sample). We found that some interacting galaxies do not follow the Tully-Fisher relation defined by the GHASP sample. The position of these galaxies in the Tully-Fisher relation can be explained by recent burst of star formation. These results will be discussed during the talk.

Lugar: Auditorium (first floor).

#### Richard I. Anderson, Observatoire de Geneve, Universite de Geneve, Switzerland

We report on our recent eight-dimensional all-sky census of Cepheids belonging to Galactic open clusters that employs spatial, kinematic, and population-specific data. Our analysis has allowed us to confirm 15 cluster Cepheids (CCs) known in the literature and to identify 5 very good candidate CCs. Details on the analysis, including data selection and homogenization are provided.

In addition to the literature data employed, we conducted observational radial velocity campaigns on both hemispheres. This program led to the discovery of the spectroscopic binary nature of at least 8 Cepheids. Some of these cases are highlighted here, including one for which a precise orbital solution was obtained.

Our data mining approach to membership has the benefit of being transparent and self-consistent, and enables ranking of membership confidence according to the probabilities computed. However, some limitations of the literature data, especially for open clusters, are apparent. These limitations are discussed in the context of a calibration of the Galactic period-luminosity relationship using our bona-fide CC sample. Our method will find application in upcoming large surveys such as LSST and Gaia.

#### Wolfgang Gieren, Departamento de Astronomía, Universidad de Concepción, Chile

I will briefly discuss the basic uncertainties in using Cepheids as tools to set up the cosmic distance scale, and to derive the Hubble constant. I will then report on the work of our group to improve on one crucial aspect of the Cepheid method, which is to determine an accurate distance to the Large Magellanic Cloud as the best-suited fiducial galaxy to measure Cepheid distances to more distant galaxies, using eclipsing binary systems in the LMC.

I will also report on an independent determination of the LMC distance from an application of the infrared surface brightness technique on LMC Cepheids, which yields a check on the distance derived from the eclipsing binaries.

#### Linda Schmidtobreick, ESO (Santiago), Chile

From our large observing campaign, we find that nearly all non- or weakly magnetic Cataclysmic Variables (CVs) in the orbital period range between 2.8 and 4 hours are of SW Sex type and as such experience very high mass transfer rates. The exceptions seem to be some old novae that have periods around 3.5 h but their spectra do not show the typical SW Sex characteristics, i.e. they do not show any sign of high mass transfer but their spectra resemble those of dwarf novae with rather low mass transfer rates.

As the evolution of CVs is driven by angular momentum loss which results in a decrease of the orbital period, all long-period CVs need to cross the SW Sex regime of the orbital period distribution before entering the gap.

This makes the SW Sex phenomenon an evolutionary phase in the life of a cataclysmic variable. The presence of old novae in this phase that do not follow the trend but show instead rather low mass transfer rates can be interpreted as evidence for the presence of hibernation effects.

#### Neil Nagar, Departamento de Astronomía, Universidad de Concepción, Chile

Phasing all of the ALMA dishes together will enable the array to function as a single telescope with effective aperture of ~85 m diameter. A phased ALMA will serve as the high sensitivity anchor of (sub)mm Very Long Baseline Interferometry (VLBI) arrays – the Event Horizon Telescope – capable of resolving supermassive black holes on Schwarzschild radius scales. At 1.3mm and 0.8mm wavelength, the Event Horizon Telescope will be able to time-resolve changing structures at the event horizon of SgrA*, search for periodic signatures of orbiting hot-spots in the innermost accretion flow, and study the launching region of extragalactic jets at Schwarzschild radius resolution. A phased ALMA will also be a sensitive pulsar/transient observatory with the ability to search for pulsars towards the Galactic Center and study known high frequency magnetars with sub-ns time resolution. First phased array science projects are expected to be carried out with ALMA within two years.

I will describe the technical and scientific goals of the ALMA Phasing Project and the Event Horizon Telescope, and UdeC Astronomy’s involvement in these.

#### Cristina Ramos Almeida, Instituto de Astrofísica de Canarias, España

I will present recent results on SED+spectroscopy fitting with CLUMPY torus models using subarcsecond resolution infrared data and a Bayesian approach. Our aim is to constrain and compare the properties of Type-1 and Type-2 Seyfert tori. Unification schemes of AGN account for a variety of observational differences in terms of viewing geometry.

However, we find evidence that strong unification may not hold, and that the immediate dusty surroundings of Type-1 and 2 Seyfert nuclei are intrinsically different in terms of covering factor. Finally, I will discuss the role of host galaxy obscuration in the fits and present our future projects on this topic.

#### Brad Gibson, Jeremiah Horrocks Institute, University of Central Cancashire, UK

The history of disk galaxy simulation is dotted with remarkable successes, tempered by frustrating impasses, including an inability to recover anything remotely similar to the Milky Way. Recent advances suggest that we might have made a breakthrough by generating essentially bulgeless disks. I will examine the evidence for this new-found optimism and identify where the shortcomings suggest we should be concentrating our future efforts.

#### Katherine Vieira, Centro de Investigaciones de Astronomía, Venezuela

It has been recently discovered that the Galactic Bulge is X-shaped, a double red clump in the color-magnitude diagram has been observed at l=0 from b=-4 to b=-8. Dynamical models describe such X structure as an extreme case of boxy-peanut bulges, in which the buckling and bending of the stellar distribution re-arrange the stars on stable banana-orbits.

Proper motions, along with radial velocities and abundances are being used to detect the streaming motions along the arms of the Bulge, that are expected for these elongated orbits. A preliminary result is being presented for a target at (l,b)=(0,-6), as well as our plans to study a list of other fields across the Bulge. The final goal is to provide observational constraints to the models of the formation of boxy-peanut bulges through dynamical instabilities.

#### Luca Sbordone, Heidelberg University

The least chemically evolved stars in the Milky Way represent arguably the most effective record of the initial phases of the assembly of our Galaxy. Their chemical composition bears the imprint of the very first nucleosynthesis events in the Universe, and of the environmental conditions in which the first star formation episodes took place. At the same time, such objects are extremely rare and difficult to identify and analyze. In this talk, I will report on the current status on an ongoing project to identify and study extremely metal poor dwarf stars in the Milky Way Halo by means of UVES and X-Shooter, starting from its initial GTO observations, leading to the discovery of the most metal-deficient star known to date (SDSS J102915+172927), and prosecuting now in the ongoing Large Program TOPoS, of which I will present the first results.