/ Seminarios


Los seminarios del Departamento de Astronomía de la Universidad de Concepción, son instancias de encuentro, intercambio de información y actualización de nuevas investigaciones astronómicas y proyectos, realizados por los miembros del Departamento y/o por astrónomos invitados que frecuentemente nos visitan.

El público que asiste a los seminarios generalmente lo componen profesores y alumnos de pregrado y postgrado del Departamento de Astronomía.

Los Seminarios son organizados por el Dr. Joerg Dabringhausen

20 de diciembre de 2016, Andromeda chained to the Box: Dynamical Models for M31 - Bulge & Bar

Matias Blana

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 14:00 hrs.

06 de diciembre de 2016, AGN and Star formation in active galaxies: a multi-wavelength review

Eleonora Sani

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 14:00 hrs.

20 de diciembre de 2016, Andromeda chained to the Box: Dynamical Models for M31 - Bulge & Bar

Matias Blana (OPINAS, MPE)

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 14:00 hrs.

13 de diciembre de 2016, Dynamical Exploration in the Core of 47 Tucanae

Javiera Parada (UBC)

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.

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 14:00 hrs.

29 de noviembre de 2016, The unexpected eccentricity of wide sdB binaries

Joris Vos

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 14:00 hrs.

25 de noviembre de 2016, The Status and Future of the APOGEE Project

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?.

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 15:00 hrs.

22 de noviembre de 2016, Is the ex-nova RR Pictoris a hierarchical triple star?

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.

Room: Auditorium,  Department of  Astronomy. Universidad de Concepción

Time: 14:00 hrs.

21 de noviembre de 2016, Bulge-Disc Decomposition with IFU data/MegaMorph...

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.

Room: Auditorio,  Departamento de Astronomía. Universidad de Concepción

Time: 15:30 hrs.

11 de octubre de 2016, Firing The Canon at the Monoceros Ring


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.”

Room: Auditorio,  Departamento de Astronomía. Universidad de Concepción

Time: 14:00 hrs.

28 de septiembre de 2016, Beyond turbulence: a fundamentally different mode of star formation in...

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.

Room: Auditorio,  Departamento de Astronomía. Universidad de Concepción

Time: 14:oo hrs.

13 de septiembre de 2016, Deriving metallicities through calcium triplet spectroscopy...

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.

Room: Auditorio,  Departamento de Astronomía. Universidad de Concepción

Time: 14:oo hrs.

23 de agosto de 2016, The statistical connection between the intergalactic medium ...

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.

Room: Auditorio,  Departamento de Astronomía. Universidad de Concepción

Time: 14:oo hrs.

16 de agosto de 2016, Sparse modeling in astronomy

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

Room:  Sala de reuniones,  Departamento de Astronomía. Universidad de Concepción

Time: 11:15 hrs.

16 de agosto de 2016, Finding the First Cosmic Explosions

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.

Room:  Sala de reuniones,  Departamento de Astronomía. Universidad de Concepción

Time: 11:15 hrs.

12 de agosto de 2016, New Solutions to Line-Driven Wind of Hot Massive Stars

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).

Room:  Auditorium Departamento de Astronomía. Universidad de Concepción

Time: 16:00 hrs.

22 de junio de 2016, Building the World’s Largest Telescopes at ESO

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 for the future.

Room:  Auditorium Profesor Alamiro Robledo, Facultad de física. Universidad de Concepción

Time: 15:00 hrs.

07 de junio de 2016, Globular clusters and the Milky Way connected by chemistry

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.

Room: Auditorium Astronomy

Time: 14:00 hrs.

31 de mayo de 2016, On the origin and evolution of galactic magnetic fields

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.

Room: Auditorium Astronomy

Tuesday, 31 May.

Time: 14:00 hrs.

17 de mayo de 2016, The formation and survival of star cluster...

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.

Room: Auditorium Astronomy

Time: 14:00 hrs.

4 de mayo de 2016, Observed thermal and maser variability in millimeter lines of ...

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

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

Time: 14:00 hrs.

26 de abril de 2016, The rich Be star phenomenology and its modelingr...

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.

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

Time: 12:00 hrs.

20 de abril, 2016, An ALMA view on the interstellar medium of the SPT sample...

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.

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

Time: 12:00 hrs.

12 de abril, 2016, The occurrence/non-occurrence of dark matter in elliptical galaxies

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

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

Time: 12:00 hrs.

15 de diciembre de 2015 -“ Investigating (x/fe) imf, and compositeness...

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

01 de diciembre de 2015 -Characterising the host galaxies of type II quasars

Patricia Bessiere  (Universidad de Concepción)

Although 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

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

30 de noviembre de 2015 -Seminario Aeree Chung

Aeree Chung (Yonsei University)


Room:  Our Auditorium (first floor, new astro-building)
Time: 15:00 hrs.

25 de noviembre de 2015 - The pillars and the twins of the stars in the Gaia-ESO Survey

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
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.

Room: Auditorio Facultad Ciencias Físicas y Matemáticas  (first floor)
Time: 14:00 hrs.

24 de noviembre de 2015 -The Infrared Properties of the Interstellar Medium in Local Luminous...

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

19 de noviembre de 2015 -Warm ISM in the SGR A Complex...

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 15:00 hrs.

17 de noviembre de 2015 -“Disks and cones: resolving the dusty torus of Active Galactic...

Konrad Tristram (ESO)

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

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

12 de noviembre de 2015 -“Be stars as seen in 2015

Thomas Ruvinius (ESO)

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 10:00 hrs.

03 de noviembre de 2015 -“Closing the foodchain of magnetic whorls...

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

27 de octubre de 2015 -“ GEMINI/GeMS Observations of Obscured Galactic Bulge ...

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

20 de octubre de 2015 -“Molecular clouds in low metallicity dwarf galaxies.

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

06 de octubre de 2015 -“The most distant quasars with Pan-STARRS1

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

Room:  Our Auditorium (first floor, new astro-building)
Time: 14:00 hrs.

25 de septiembre de 2015 -“Atacama Large Millimeter/submillimeter Array (ALMA)...

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

Room:  Our Auditorium (first floor, new astro-building)
Time: 17:00 hrs.

26 de agosto de 2015 -“Massive multiplex MUSE spectroscopy in globular clusters

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 10:00 hrs.

03 de agosto de 2015 -“Probing the origin of the high-energy emission in active galactic...

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.

Room:  Our Auditorium (first floor, new astro-building)
Time: 16:00 hrs.

09 de julio de 2015 -“Disentangling/Deconvolving stellar rotational velocities

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.

Room:  Auditorium (first floor)
Time: 11:00 hrs.

07 de mayo de 2015 -“ New model of strong magnetic fields in magnetars

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.

Room:  Auditorium (first floor)
Time: 15:30 hrs.

23 de abril de 2015 -“ The Role of Dwarf-Dwarf Interactions in the Evolution of Low Mass Galaxie

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.
Room:  Auditorium (first floor)
Time: 16:00 hrs.

07 de abril de 2015 -“Plays of polarized light in the dusty nebula of the long period Cepheid RS Puppis

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
Room:  Auditorium (first floor)
Time: 15:30 hrs.

02 de abril de 2015 -“The birth of a giant star forming clump in a disk galaxy at redshift z = 2

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 miniature 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…
Room:  Auditorium (first floor)
Time: 16:00 hrs.

01 de abril de 2015 -“Anatomy of an X-ray detected cluster at z = 2: low metallicities and enhanced ...

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.

Room:  Auditorium (first floor)

Time: 16:00 hrs.

9 de enero de 2014 -“Characterizing Cosmic Dawn through Observations of the 21-cm line

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.
Room:  Auditorium (first floor)
Time: 11:00 hrs.

16 de marzo de 2015 -“Not-so-simple stellar populations in Local Group star clusters

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.
Room:  Auditorium (first floor)
Time: 16:00 hrs.

9 de enero de 2014 -“Characterizing Cosmic Dawn through Observations of the 21-cm line

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.
Room:  Auditorium (first floor)
Time: 11:00 hrs.

7 de enero de 2014 -Lurking the SSA22 field with multi-slit spectroscopy

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
Room:  Auditorium (first floor)
Time: 17:00 hrs.

5 de diciembre de 2014 -Peering into the Hearts of the Most Luminous Local Galaxies...

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
Room:  Auditorium (first floor)
Time: 11:00 hrs.

27 de Noviembre de 2014 -Tracing light: trails of galaxy evolution...

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)…
Room:  LF207 (ground floor)
Time: 15:00 hrs.

14 de Noviembre de 2014 -Dust Growth in Protoplanetary Disks: the First Step Towards Planet Formation.

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
Room: Auditorio (ground floor)
Time: 11:00 hrs.

13 de Octubre de 2014 -he High cadence Transient Survey (HiTS): real-time...

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.

Room: Auditorio (ground floor)
Time: 15:00 hrs.

6 de noviembre de 2014 - The Large Latin American Millimeter Array (LLAMA)

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).

Room: Auditorium (first floor)
Time: 15:00 hrs.

3 de noviembre de 2014 -The Dynamics and Cold Gas Content of Luminous Infrared Galaxy Mergers in Unive..

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.
Room: Auditorio (ground floor)
Time: 17:00 hrs.

30 de Octubre de 2014 -Globular Clusters and Nuclei in Dwarf Elliptical Galaxies

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.
Room: Auditorium  (first floor)
Time: 17:00 hrs.

22 de Octubre de 2014 -The slow quenching of star formation in Milky Way-like..

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.
Room: Auditorio (ground floor)
Time: 16:00 hrs.

9 de Octubre de 2014 -Proper motions in the Galactic Bulge and Multiple Stellar...

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.
Room: Auditorio (ground floor)
Time: 11:00 hrs.

6 de Octubre de 2014 -Powerful quasar.feedback in local and very distant (u) LIRGs

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).
Room: Auditorio (ground floor)
Time: 17:00 pm

9 de octubre de 2014 - Higher Dimensional Black Holes in General Relativity

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.

3 de Abril de 2014 - Optical and Infrared studies of Be stars

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.

10 de Marzo de 2014 - Stellar dynamics and galactic nuclei:...

…Testing mass segregation with red giants and the connection with GR

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″.

7 de Marzo de 2014 - The Lithium content of ancient stellar populations and in giant stars

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.

27 de Enero de 2014 - New results on galaxy evolution in dense environments from SpARCS,...

…the Spitzer Adaptation of the Red-sequence Cluster Survey

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.

23 de Enero de 2014 -Isolated elliptical galaxies, Galactic globular clusters and the Sagittarius dwarf

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.

17 de Enero de 2014 - Radio supernovae in the (circum-)nuclear regions of luminous infrared galaxies

Cristina Romero Cañizales

The so called luminous infrared galaxies (10^11 L_sun < L_IR < 10^12 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.

9 de Enero de 2014 - Starburst-AGN mixing in NGC 7130

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.

12 de Diciembre de 2013 - Star Clusters as Probes of Evolution of Galaxies

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

10 de Diciembre de 2013 - Introduction to the Gemini South Adaptive Optics Imager (GSAOI)

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.

5 de Diciembre de 2013 - Explorando nuevos horizontes en NASA: Marte, Luna y planetas extrasolares

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 próximos 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).

13 de Noviembre de 2013 - Star formation & galaxy kinematics across the Universe

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.

12 de Noviembre de 2013 - The Green Valley is a Red Herring: How, when and...

…why galaxies quench their star formation

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.

28 de Octubre de 2013 - IMF variations in UCDs (ultra compact dwarf galaxies)

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.

23 de Octubre de 2013 - Kinematics and chemical elements of the very metal...

…poor Globular Cluster NGC 4372

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.

15 de Octubre de 2013 - Improving Quasar Black Hole Mass Estimates

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.

26 de Septiembre de 2013 - Physical and chemical properties of molecular gas in the centre of galaxies

Rebeca Aladro

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.

5 de Septiembre de 2013 - The Formation and Evolution of the Faintest Dwarf Spheroidal Galaxies

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.

19 de Agosto de 2013 - Introduction to Sloan Digital Sky Survey IV, and the Status of...

..the APOGEE-1 and -2 Projects

Steve Majewski, University of Virginia, Estados Unidos

5 de Agosto de 2013 - The double RGB in M2 seen through low-resolution MODS spectroscopy

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.

28 de Junio de 2013 - Disclosing the faint universe

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.

21 de Junio de 2013 - What has variability taught us about the central engine of AGN

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.

20 de Junio de 2013 - Super-massive black hole binaries in gas-rich environments

Jorge Cuadra, Santiago, Chile

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.

14 de Junio de 2013 - Welterweights in space - Intermediate-mass black holes

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.

10 de Junio de 2013 - A kinematic analysis of Hickson Compact Group galaxies:...

since perturbed rotation curves to the Tully-Fisher relation

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.

27 de Mayo de 2013 - Cepheids in Galactic Open Clusters: An All-sky Census in 8D

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.

6 de Mayo de 2013 - Improving the accuracy of the Cepheid method to determine the Hubble constant:...

A precision distance to the LMC

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.

2 de Mayo de 2013 - Constraining the CV evolution with SW Sex stars and old novae

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.

22 de Abril de 2013 - The Event Horizon Telescope:...

Imaging Black Hole Shadows at Scharwarzschild radius Resolution

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.

3 de Abril de 2013 - Testing the Unification Model for AGN in the Infrared

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.

25 de Marzo de 2013 - Spirals with Supercomputers: Have We Finally Got it Right?

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.

14 de Marzo de 2013 - Using proper motions to solve for the X in the Galactic Bulge

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.

9 de Enero de 2013 - Searching for the most primitive stars with X-Shooter and UVES

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.