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2016 Astronomy Talks

2016 UNAB-UDP Seminar Series

2015 UNAB-UDP Seminar Series

2014 UNAB-UDP Seminar Series

Other Talks at UDP

2016 UNAB-UDP Seminar Series

Date Speaker Title/Abstract Location
Friday
08/04

11:30am
Jeff Wagg
SKA Telescope
The Square Kilometre Array
The world is uniting in order to build one of the largest and most ambitious scientific facilities that has ever existed. Consisting of two telescopes in Australia and South Africa, the Square Kilometre Array (SKA) will answer fundamental questions related to the nature of the Universe and our place within it. From spinning neutron stars to black holes at the edge of the Universe, the SKA will challenge the theories put forward by Einstein. I will describe the status of the ongoing SKA design work and present an overview of some of the questions that the SKA will help to answer.
UDP
Sala de Titulación, Facultad de Ingeniería, Av. Ejército 441
Friday
29/04

11:30am
David Principe
Universidad Diego Portales
Observing the Circumstellar Environment of the Eruptive FUor/EXor Protostar V1647 Ori with ALMA
Fu Ori (FUor) and EXor objects represent a short-lived stage of protostellar evolution characterized by intense mass accretion events which cause extreme variability in the form of outbursts. While it is well demonstrated that these objects exhibit sudden outbursts (Delta V~2-6), the mechanism causing such variability is not well understood. High spatial and spectral resolution observations of the circumstellar environment of these objects are essential to distinguish between different outbursting mechanisms. We present ALMA observations of the FUor/EXor object V1647 Ori as part of an ALMA campaign, which has observed a combined eight FUor and EXor type objects. Deeply embedded in the dark cloud LDN 1630 (L1630), V1647 Ori is one of a few FUor/EXor objects to have been extensively studied at multiple wavelengths before, during and after an outburst. We present preliminary results derived from ALMA 12CO, 13CO, C18O and continuum observations of the circumstellar environment of V1647 Ori. By measuring gas/dust masses and gas kinematics of the circumstellar disk, we investigate the potential mechanisms producing variability in these eruptive protostars during an essential, yet rarely observed, stage of pre-main sequence stellar evolution.
UNAB
Fernandez-Concha 700
Friday
06/05

3:00pm
Andreas Reisenegger
Pontificia Universidad Católica de Chile
Gravitational waves: a new channel of information from the Universe
The detection of gravitational waves by the LIGO experiment is one of the main scientific results of recent times. The purpose of this colloquium is to explain the historical context, what gravitational waves are, what was measured, and what to expect in the near future.
UDP
Auditorio de la Facultad de Ingeniería, Av. Ejército 441
Friday
13/05

11:30am
Christopher S. Kochanek
The Ohio State University
A Search for Failed Supernovae with the Large Binocular Telescope
At the ends of their lives, stars roughly more than 10 times the mass of our Sun undergo “core collapse” when the mass of their iron cores reaches 1-2 times the mass of our Sun. In the majority of cases, this then drives a supernova explosion. While we observe many such explosions, there is no observational or theoretical requirement that all massive stars explode. I will review the evidence that 10-30% of the time, core collapse instead leads to a “failed” supernova, producing a black hole without a dramatic external explosion. Then I will describe our search for failed supernovae using the twin 8.4m Large Binocular Telescope and the properties of our first candidate.
UDP
Sala de Titulación, Facultad de Ingeniería, Av. Ejército 441
Friday
20/05

11:30am
Maja Vuckovic
Universidad de Valparaíso
Hot subdwarf stars as a critical test for binary stellar evolution
The hot subdwarf stars are core helium burning stars with extremely thin hydrogen envelope and a mass close to the helium core flash mass ~0.47 M☉. These extreme horizontal branch stars are low mass white dwarf (WD) precursors. To date, the precise age and evolutionary history of these stars are unknown. As a significant fraction of them are found in binaries the competing formation theories involve close binary interactions. Depending on the mass ratio, schemes such as common-envelope ejection, Roche-lobe overflow and mergers are being proposed. Currently, over 100 hot subdwarf stars are found to reside in short-period binaries with periods ranging from 1 hour to several days, with companions being either WD or M-dwarf stars. Such short-period systems have formed through binary mass transfer followed by the common-envelope ejection. Establishing the accurate masses of both components of post-common envelope binaries is the only way to empirically constrain the efficiency parameters of common-envelope ejection phase. Furthermore, detailed investigation of hot subdwarf binaries is crucial in order to determine their masses for comparison with the theoretically proposed evolutionary channels as well as to test the binary-population synthesis models.
UNAB
Campus Casona Las Condes, Fernandez-Concha 700
Friday
03/06

11:30am
Médéric Boquien
Universidad de Antofagasta
Everything you always wanted to know about measuring star formation in galaxies but where afraid to ask
Knowing when, where, and how stars form across cosmic times is key to fathom the formation and the evolution of galaxies. But are we so sure we measure star formation rates precisely and accurately? Shouldn’t we actually worry about how we get star formation rates? In the first part of this talk, I will show that if many star formation rate estimators are now available across the electromagnetic spectrum, they each possess their own caveats and often provide us with an inconsistent view of star formation in galaxies. In particular, I will describe the sometimes startling effect of old stars on star formation rates estimates and the worrisome impact of some (surprisingly) strong assumptions behind some popular star formation rate estimators. In a second part I will present a new effort to build modern and resilient star formation rate estimators. I will focus on the so-called hybrid estimators that combine the ultraviolet emission from short-lived massive stars and the emission of the dust heated by these stars. Using the CIGALE multi-wavelength modeling tool, I will show that we can build adaptive star formation rate estimators that make them immune to some of the issues plaguing classical hybrid star formation rate estimators.
UDP
Av. Ejército 441
Friday
17/06

11:30am
Javier Alonso
Universidad de Antofagasta
The inner Galactic globular clusters
Although most globular clusters in the Milky Way are interior to the solar circle, the globular clusters located towards the inner Galaxy have been historically neglected due to the limitations imposed in their study by the existence of large extinctions in their lines of sight. In my talk I will present a series of different novel approaches that we are developing and using to extract the relevant information about the physical parameters of these objects. I will also show interesting by-products of these analyses that can allow us to better understand the characteristics of the interstellar medium in the low-latitude lines of sight towards these clusters.
UNAB
Fernandez-Concha 700
Friday
01/07

11:30am
Valentino Gonzalez
Universidad de Chile
Galaxy Growth in the Early Universe
As the Universe evolves, the structures in it grow in mass with a rate that has been steadily decreasing since very early on. The first 2 billion years represent an epoch of very fast evolution and growth for galaxies. The study of this process in distant galaxies requires extremely deep data that nowadays is only available thanks to the Hubble Space telescope and, very importantly, to Spitzer. Based on the deepest images from these two powerful telescopes today we can study the physical properties of these galaxies such as their ages, star formation rates, and stellar masses. By following the evolution of these properties in the early Universe, we are starting to understand the very first stages of galaxy evolution and the stellar mass growth in galaxies. In this talk I will review some of the most recent progress in this field, the current challenges that we face (e.g., the effect of strong emission lines in SED modeling, and their implications), and some alternatives that we are exploring to move forward.
UNAB
Fernandez Concha 700
Friday
15/07

11:30am
Doug Geisler
Universidad de Concepción
Multiple Populations in Star Clusters
I will give a brief introduction to the subject and focus on recent work undertaken by our group in Concepcion to investigate observationally the presence and nature of multiple populations in star clusters in the Galaxy and Magellanic Clouds.
UNAB
Fernandez-Concha 700
Friday
22/07

11:30am
Ricardo Salinas
Gemini Observatory
Multiple populations and/or stellar variability in globular clusters
Globular clusters (GCs) continue to be a treasure chest where many astrophysical processes can be tested. One of the main drivers of GC studies in the last years has been the discovery of multiple stellar populations, against the long-held belief of them as the canonical single stellar populations. One remaining uncertainty is whether a cluster mass threshold exists for the generation of a second population. In this talk I will show our search for multiple populations in one of the least massive GCs in our Galaxy, E3. In the LMC GCs, extended main sequences, initially considered as multiple populations, have been now rather interpreted as a signature of stellar rotation. Our group has introduced the novel idea that extended main sequences could actually be produced by a large number of variables at the main sequence turn-off level. I will show whether this hypothesis works in the case of NGC 1846. Finally, I will end this talk discussing new results on stellar variability in globular clusters using adaptive optics.
UDP
Av. Ejército 441
Friday
05/08

11:30am
Cristobal Petrovich
CITA
On the origin of hot and warm Jupiters
The first exoplanet discovered in a main sequence star was a hot Jupiter (Peg b in 1995). After ~20 years of research and the discovery of >600 gas giant planets, the origin of the close-in Jupiters remains a fundamental and highly debated open problem in planet formation. First, I will review our current understanding from the orbital architecture of the planetary systems with hot Jupiters (periods <10 days) and warm Jupiters (periods ~10-100 days), and how these constrain different formation mechanisms. Second, I will show that planet-planet interactions coupled with tidal friction has the potential to reproduce the orbital architecture of most of the hot Jupiters and a population of eccentric warm Jupiters. Finally, I will describe two predictions from our model that can be tested in upcoming surveys.
UDP
Av. Ejército 441
Friday
19/08

11:30am
Sebastian Lopez
Universidad de Chile
Probing the circum-galactic medium with lensed quasars
Lensed quasars probe the spatial structure of intervening absorbers on galactic scales. I will present new echelle data on MgII systems at separations of 0.1 to 100 kpc and redshifts 0.5
UNAB
Fernandez Concha 700
Friday
16/09

11:30am
Amit Vishwas
Cornell
Submillimeter Instrumentation & ISM Studies of Galaxies in the Early Universe with far-IR Fine-Structure Emission Lines
Understanding the interstellar medium (ISM) of galaxies is paramount for developing insights to the formation of galaxies in the Universe. Studies of the ISM in high redshift galaxies have progressed tremendously in the past years, but studies of the physical properties based on a suite of fine structure lines are still in their beginning stages. With observations of the fine structure lines of C, N, and O, enabled by our 1st and 2nd generation High Redshift (z) and Early Universe Spectrometers (ZEUS-1 & 2), we are tracing the build up of first metals and studying energetics and feedback mechanisms to address the initial stages of galaxy evolution between z~1-5. We have recently started a survey of / with ZEUS-2 at APEX, I will present initial results from our observations that reveal extreme physical conditions of the ISM, young starbursts and rapid gas depletion timescales in some of the brightest galaxies in the early Universe.
UDP
Av. Ejercito 441
Friday
14/10

11:30am
Roberto Assef
UDP
Hot, Dust-Obscured Galaxies
The WISE mission has discovered a rare population of high-redshift, hyper-luminous infrared galaxies, all with bolometric luminosities above log L_Bol/L_Sun > 13 , and many with log L_Bol/L_Sun > 14. Selected by their extremely red mid-IR colors and shown to have very hot dust temperatures, these hot, dust-obscured galaxies, or Hot DOGs for short, are dominated by the emission of a highly obscured, actively accreting supermassive black hole and may probe a key stage in galaxy evolution. I will present the latest results of our ongoing research to understand the nature of these enigmatic objects from the point of view of our extensive X-ray through radio photometric and optical spectroscopic follow-up observational campaigns. I will put emphasis on recent results from ALMA observations on W2246-0526, the most luminous Hot DOG, that revealed that the ISM gas is in an extreme, highly turbulent state, possibly being expelled from the host galaxy by the radiation from the AGN.
UNAB
Fernandez Concha 700
Friday
21/10

11:30am
Vera Könyves
CEA/Saclay
Star-forming dense cores and filaments from nearby molecular clouds to massive regions with Herschel and ArTéMiS
Herschel observations of nearby molecular clouds, up to a distance of ~500 pc, suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. These observations support a picture for low-mass star formation, according to which the dissipation of kinetic energy in large-scale MHD flows generates a quasi-universal filamentary structure in the ISM, and then prestellar cores arise from gravitational fragmentation of the densest filaments. The validity of this scenario in high-mass star-forming regions is still an open question. However, recent surveys with Spitzer and Herschel also suggest that star formation in dense molecular gas is governed by essentially the same “laws” in nearby Galactic clouds and distant external galaxies. Among other ground-based telescopes, we also use the ArTéMiS bolometer camera at 350 microns on APEX to map filamentary regions beyond the nearby molecular cloud complexes.
UDP
Av. Ejército 441
Friday
28/10

11:30am
Robert Kennicutt
Cambridge
From Gas to Stars
Studying the formation of stars on galactic scales offers vital clues for the understanding of star formation itself, and as critical input physics for understanding the formation and evolution of galaxies. The past decade has witnessed a revolution in our ability to measure star formation rates of galaxies, and map their properties across the Hubble sequence, across cosmic time, and as functions of the underlying physical properties of the interstellar medium. These lectures will introduce the multi-wavelength toolbox that is now available for measuring the star formation properties of galaxies, and review the demographics of the star forming galaxy populations in the present-day and early Universe.
UDP
Av. Ejército 441
Friday
04/11

11:30am
Lorenzo Monaco
UNAB
The Lithium content of globular clusters
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. Globular clusters 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 the WMAP and the Plank satellites. I will present the results of the spectroscopic investigation on the lithium content among unevolved stars in the globular clusters WCen and M4 and among giant stars in M54.
UNAB
Fernandez Concha 700
Friday
18/11

11:30am
Angela Hempel
UNAB

Friday
02/12

11:30am
Amelia Bayo
Universidad de Valparaíso

 

Other Talks at UDP

Date Speaker Title/Abstract Location
Monday
18/01

11:30am
Gabriel Brammer
STScI
Crónica de una Muerte Anunciada: The Discovery and Reappearance of the Gravitationally-lensed Supernova 2014/2015 Refsdal
Supernova Refsdal was discovered in Nov 2014 in Hubble Space Telescope imaging of the galaxy cluster MACS J1149.6+2223, multiply imaged by an early-type cluster member (z=0.54) into an Einstein cross resolved into four subimages. The properties of SN Refsdal (z=1.49) are consistent with those of a SN1987A-like peculiar type II explosion, based on its slowly-rising lightcurve and observed broad H-alpha emission associated with the supernova. The host galaxy of the supernova is itself multiply imaged in three well-separated images by the massive foreground cluster. With constraints based on measurements of the time delays of the four Refsdal images along with spectroscopic redshifts of additional multiply-imaged background galaxies in the field, we undertook a modeling effort to predict the time delay of the reappearance of the SN in the third host image closest to the core of the foreground cluster potential. Time delay predictions from different teams using qualitatively different lens modeling techniques suggested that the SN should appear between late 2015 and early 2016, and indeed, the new image was detected in monitoring observations taken on 11 Dec 2015. The remarkable configuration of SN Refsdal has provided a valuable tool for testing cluster dark matter models. Multiply-imaged SNe in galaxy-scale lenses detected in future wide-field surveys such as LSST are promising avenues for obtaining cosmological constraints (e.g., H0) originally envisioned by Refsdal in 1964.
UDP
Sala de Titulación, Núcleo de Astronomía, Av Ejército 441
Thursday
30/06

11:30am
Rainer Schoedel
Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain
GALACTICNUCLEUS – a high-angular resolution, near-infrared study of the Galactic centre
Because of the unique observational challenges – extreme crowding and extinction – any existing large-scale near-infrared (NIR) imaging data on the Galactic Center (GC) are limited by either one, or a combination, of the following: saturation, lack of sensitivity, too low angular resolution, or lack of multi-wavelength coverage. To overcome this situation, we are currently carrying out a sensitive, 0.2” resolution JHK imaging survey of the Galactic Centre with HAWK-I/VLT. Thanks to holographic imaging, we achieve a similar resolution than with HST/WFC, but can cover also the long NIR, beyond 2 microns, which is essential to deal with extinction. Our survey is supported by an ESO Large Programme and will provide photometrically accurate (few percent uncertainty for H<18 stars), high-angular resolution, NIR data for an area of several 100 pc^2, a more than ten-fold increase compared to the current state of affairs. Here we present and overview and first results.
UDP
Facultad de Ingenieria, Av. Ejercito 441
Tuesday
04/10

11:30am
Mark Lacy
NRAO
The Many Faces of AGN feedback
Models of galaxy formation seem to require winds and/or jets from AGN to cut off star formation at high masses, and to reproduce the observed correlation of black hole mass and bulge mass. In this talk I will discuss some observational results on several different ways in which AGN can provide feedback to its host galaxy, using VLA, ALMA and infrared data. I will then try to summarize the remaining uncertainties in how feedback works, and discuss which mechanism ultimately dominates.
UDP
Av. Ejército 441
Monday
24/10

11:30am
Xian Chen
PUC
The gamma-ray afterglows of tidal disruption events
Stars becoming too close to a supermassive black hole will be tidally disrupted. Part of the stellar debris would collide into each other and produce a luminous flare. So far about 40 such “tidal disruption events” have been detected. In this talk, I will show that the same events also radiate long-lasting gamma-ray emission, because of the interaction between the stellar debris and the surrounding interstellar medium. Such a emission could be detected by the Cherenkov Telescope Array, part of which is planned to be built in Chile. Without careful discrimination, these sources potentially could contaminate the searches for starburst galaxies, galactic nuclei containing millisecond pulsars or dark matter annihilation signals.
UDP
Av. Ejército 441