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2017 Astronomy Talks

2017 UNAB-UDP Seminar Series

2016 UNAB-UDP Seminar Series

2015 UNAB-UDP Seminar Series

2014 UNAB-UDP Seminar Series

2017 UNAB-UDP Seminar Series

Date Speaker Title/Abstract Location
Friday 06/01
11:30am
Roberto Decarli
MPIA Heidelberg
The birth of the giants: massive galaxies at the dawn of cosmic time
The presence of a population of massive (>1e11 Msun), `red-and-dead’ galaxies at redshift z~4 (age of the Universe: 1.5 Gyr) implies intense star-formation episodes already in place at z>6 (age of the Universe: < 1 Gyr). Deep field investigations unveiled an abundant population of small (<1e9 Msun), star-forming (SFR=0.1-1 Msun/yr) galaxies at z>6. These galaxies dominate the cosmic star-formation budget at these early epochs, and possibly drive the reionization of the Universe. However, they are by far too small to account for the massive, quiescent galaxies found at z~4. The only known examples of starbursting galaxies at z>6 are, with only one exception, QSO host galaxies. In this talk I will review on-going efforts to discover and characterize these extremely luminous sources, and highlight the lessons we have learned from them in the context of the formation and first evolution of massive galaxies.
UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
31/03

11:30am
Amelia Bayo
Universidad de Valparaiso
First millimeter detection of the disk around a young, isolated, planetary-mass object
OTS44 is one of only four free-floating planets known to have a disk. We have previously shown that it is the coolest and least massive known free-floating planet (∼12 MJup) with a substantial disk that is actively accreting. We have obtained Band 6 (233 GHz) ALMA continuum data of this very young disk-bearing object. The data shows a clear unresolved detection of the source. We performed radiative transfer modeling of the full SED of the object and obtained disk mass estimates via empirical correlations derived for young, higher-mass, central (substellar) objects. The range of values obtained are between 0.07 and 0.63 M⊕ (dust masses). We compare the properties of this unique disk with those recently reported around higher mass (brown dwarfs) young objects in order to infer constraints on its mechanism of formation. While extreme assumptions on dust temperature yield disk-mass values that could slightly diverge from the general trends found for more massive brown dwarfs, a range of sensible values provide disk-masses compatible with a unique scaling relation between Mdust and M∗ through the substellar domain down to planetary masses.
UDP
Sala de Titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
21/04

11:30am
Francisco Forster
Universidad de Chile/MAS
The High cadence Transient Survey: astrophysics and data science at large etendue and high cadences
The High cadence Transient Survey (HiTS) is a survey that uses DECam to detect and follow-up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera and a custom pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. I will discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014, and 2015 campaigns we detected more than 120 young SN candidates. We did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, but we are able to constrain the complex outermost regions of RSG atmospheres through their shocked signature. The unique combination of cadence and etendue of HiTS made this dataset a rich playground for other astrophysical variability studies and data analysis techniques. In a data driven and interdisciplinary approach we have found thousands of moving asteroids, hundres of RR Lyrae and other variable stars, tried new methods for classifying these sources, for detecting transient objects using deep learning, for detecting transients based on image streams using Kalman filter and correntropy, and for constraining physical parameters in a Bayesian approach. Finally, I will highlight the implications of this work for future massive data sets produced by astronomical observatories, such as LSST.
UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
05/05

11:30am
Claudia Cicone
INAF – Osservatorio Astronomico di Brera
Observations of molecular gas in normal star-forming galaxies
The cold phase of the interstellar medium has a central role in galaxy growth and evolution. In normal galaxies following the so-called “main sequence” of star-forming galaxies, the star formation rate is believed to be regulated uniquely by the amount of gas available, and more specifically by the mass of cold and dense molecular gas. Despite the enormous efforts to trace molecular gas in larger and larger samples of galaxies, at multiple scales and at multiple epochs, nearly all of our empirical knowledge of scaling relations linking molecular gas and galaxy properties is still based on observations of massive (e.g. M*>10^10 M_Sun), metal-rich and gas-rich spirals. There is therefore a strong motivation to test molecular gas scaling relations over a much broader dynamic range of galaxy properties. With this goal in mind, we have undertaken the “APEX low-redshift legacy survey of molecular gas (ALLSMOG)”, a survey of CO(2-1) line emission in a sample of ~100 normal star forming galaxies in the local Universe, characterized by stellar masses (10^8.5<M*[M_Sun]<10^10), SFRs and gas-phase metallicities significantly lower than have been probed by previous CO observations. The survey was completed in early 2016 and the final data products will be released soon (Ciconeet al. submitted). I will present our latest results based on the full ALLSMOG dataset.
UDP
Sala de Titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
19/05

11:30am
Leopoldo Infante
Pontificia Universidad Católica de Chile
Astro-Engineering in Chile: The Experience of AIUC
In this talk I will present the UC Center of Astro-engineering, the logic of its creation and its projection in Chile. The mission of the center is to channel leading research and generate new technological and computational opportunities in the field of astronomy and engineering. AIUC members are academics and researchers from the UC Institute of Astrophysics and the UC School of Engineering and a group of professionals in the field of technology management. The main research lines of the center are: Optical, infrared and millimetric astronomical instrumentation, adaptive optics, numerical simulations, data mining, “Big Data”, data processing and astronautics.
UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
02/06

11:30am
Todd Thompson
The Ohio State University
Physics and phenomenology of galactic winds
Galactic winds are a crucial ingredient in galaxy evolution, but the physics of the ubiquitous outflowing high velocity gas seen from rapidly star-forming galaxies remains unknown. I will describe a series of projects designed to shed light on these open questions, with a focus on how to produce cool atomic and warm photo-ionized gas at high velocities. One idea is to precipitate the cool gas from the super-heated hot phase on scales outside the host galaxy. Another option is to directly accelerate the cool gas from the galaxy with momentum injection, perhaps provided by radiation pressure on dust or a putative fast, hot wind. I’ll highlight challenges on both the observational and theoretical fronts, and connect to observational constraints on physical scales ranging from the host galaxy’s molecular clouds to its circumgalactic medium.
UDP
Auditorio, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
09/06

11:30am
Manuela Zoccali
Pontificia Universidad Católica de Chile
The two metallicity components of the Galactic bulge
I will summarize various independent observational evidences about the presence of two different stellar components in the galactic bulge. The two differ by mean metallicity, alpha element ratios, kinematics and spatial distribution. They might have had a very different origin, or, as recently proposed, they might be the result of a secular process that funneled to the Galaxy central region stars whose properties were different, as time went by. In any case, these recent observational constraints must be met by any bulge formation model.
UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
07/07

11:30am
Cristina Romero-Cañizales
Universidad Diego Portales
An extinction-free view of merging galaxies and their constituents
The interaction of gas rich galaxies via mergers or close encounters can give rise to sudden, violent star formation (SF), often accompanied by the presence of an AGN. The merger gives rise to a system whose energy is mostly emitted in the IR with a luminosity above 10E11 L_sun. These dusty environments are the scenery of supernova explosions at a high rate as well as of super-massive black hole (SMBH) growth and at the same time, they represent excellent laboratories to study the evolution of galaxies. In this talk I will guide you trough a journey of the different science that can be done when studying mergers and I will present exciting observations on a “baby” AGN and a tidal disruption event.
UDP
Sala de Titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
21/07

11:30am
Lucia Guaita
Universidad Diego Portales
Does the escape of Lya photons in star-forming galaxies depend on HI properties?
Lyman alpha (Lya) emitters (LAEs) provide our best opportunity to study low-mass galaxies experiencing active phases of star formation. Lya photons are scattered by HI atoms and therefore LAEs could be used as tracer of the HI distribution and kinematics. Insights in the propagation and escape of Lya photons can be obtained studying local star-bursts. However, LAEs have been detected at any redshift and their properties are not homogeneous.We selected a sample of 2 < z < 4 LAEs from the VUDS (VIMOS Ultra Deep Survey) survey and I will present how scattering and HI kinematics, such as star-formation outflows, can affect the escape and large-scale propagation of Lya photons. This can have implications for the LAE evolution and also for the understanding of the galaxy properties at the epoch of re-ionization.
UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
11/08

11:30am
Amelia Stutz
Universidad de Concepción
Cluster formation in Orion: the slingshot mechanism
By observationally scrutinizing the nearest cluster in formation, we gain new insights into cluster formation physics. The Integral Shaped Filament (ISF) is home to the nearest significant protocluster, the Orion Nebula Cluster (ONC). Based on a high density of observables of both the gas and stars, we previously proposed the “slingshot” mechanism, requiring that the gas ISF oscillate ejecting stars. The B-field morphology (helical) and strength, compared with the gas mass distribution, indicates that magnetic instabilities may be propagating through the cloud driving the oscillations in the ISF. These may be responsible for the slingshot. In recent work we investigate the slingshot effect on the ONC structure. We show that the stellar density follows a Plummer profile with inner softening scale a=0.36 pc, while the gas follows a cylindrical power law. The stellar contribution to the gravitational field is nearly equal to that of the gas at r=a. At all other radii the field is gas-dominated. The cluster crossing time is ~ 0.5 Myr, nearly identical to the filament oscillation timescale. These results reveal an intimate connection between the stars and the gas, such that tidal effects due to filament oscillations may set the protocluster structure. That is, the gas density regulates the star density in the ONC. We suggest that star clusters that form in oscillating filaments are ultimately ejected, thereby terminating their formation phase, much like the “slingshot” for protostars.
UDP
Sala de Titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
25/08

11:30am
Dominik Schleicher
Universidad de Concepción
The formation of the first stars and black holes
The first stars in the Universe have formed from a primordial gas, consisting only of hydrogen and helium. Under these conditions, one of the main coolants was molecular hydrogen, which could cool the gas temperatures however only to typical temperatures of about 300 K. Due to these high temperatures, the accretion rates and thus the masses of the first stars are generally expected to be much larger than for present-day stars. I will discuss the current constraints on early Universe star formation based on the results of stellar archeology, and present results from numerical simulations where we investigated the transition from massive Pop. III stars to a lower-mass star formation mode. I will further present possible pathways to form the progenitors of the first supermassive black holes.
UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
08/09

11:30am
Sebastian Lopez
Universidad de Chile
MUSE gravitational-arc tomography of the z=1 circum-galactic medium
I will report on our recent MUSE observations of bright gravitational arcs to map the spatial distribution of the z=1 CGM. I will discuss our results and argue that this technique opens a new window in absorption-line studies of the high-redshift universe.
UDP
Sala de Titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
27/09

11:30am
Wanda Diaz-Merced
South African Astronomical Observatory Office of Astronomy for Development of the IAU
Sound to enrich time series current data analysis techniques?
Sonification is to convey information using mainly non-speech sound. This research presents the use of sonification techniques as an adjunct to visualization to enrich current data analysis techniques. Current analysis techniques for astrophysics numerical data are based on scrutinizing the data with the eyes. Astrophysics data sets acquired from the natural lab of the interstellar medium may contain events that may be masked by noise, fleeting, non persistent etc, making it difficult to identify. Results of focus group, Exploration and characterization (heard events validation) of data is presented and its application to decompose the data set into different components (frequency, oscillatory modes, etc…) of interest.
UDP
Sala de titulacion, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
13/10

11:30am
Erkki Kankare
Queen’s University Belfast
A population of highly energetic transient events in the centres of active galaxies
We have uncovered a population of luminous optical narrow-line transients coincident with the nuclear region of Seyfert galaxies. Based on extensive spectrophotometric follow-up, we exclude an AGN flare or changing-look quasar origin. Based on the integrated energy output and spectral evolution over a time scale of several years, we converge on two possible paths of origin: a tidal disruption of a star by a supermassive black hole, or an extremely energetic supernova occurring in the Seyfert galaxy narrow-line region. The former scenario would require invoking a new and hitherto unseen variant of a tidal disruption, while the latter would require an extremely efficient conversion of kinetic energy via shock interaction between the supernova ejecta and the dense ambient medium. It is likely that transient surveys have overlooked this population of events due to the incorrect contextual association with normal AGN activity.
UDP
Auditorio, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
10/11

11:30am
Beth Willman
LSST Deputy Directorm, Steward Observatory
LSST UNAB
Auditorio Campus Casona Las Condes, Fernández Concha 700
Friday
24/11

11:30am
Tom Richtler
Universidad de Concepcion
Gas and dust and MUSE in Fornax A
The dust structures in NGC 1316 (Fornax A) are so prominent that Harlow Shapley mistook them for plate defects. Generally, dust in early-type galaxies is understood as being of external origin, indicating previous infall. NGC1316 indeed has the reputation of being a merger remnant.I report on ongoing work, based on VLT/MUSE data, that strongly argues for an internal(!) origin. Dust and gas, both ionised and neutral, are intimately coupled. Many dusty features are clearly visible in the interstellar NaI-absorption. NaI even shows patchy emissions which is very rare for nearby galaxies. Since young stellar populations which could have produced the dust, do not exist, the dust is probably formed in a nuclear wind. We suggest that this is a general explanation for the ubiquitous occurrence of central dust in elliptical galaxies. We also question the character of NGC 1316 as a merger remnant.
UDP
Sala de titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441

 

Other Talks at UDP

Date Speaker Title/Abstract Location
Friday
01/09

11:30am
Eduardo Bañados
Carnegie Observatories
Quasars in the epoch of reionization
A prime objective of observational astrophysics is to characterize the earliest sources in the first Gyr of the universe, and to peer into the cosmic times when the first stars, black holes and galaxies formed. Although galaxy candidates are now identified up to redshifts of about 10, their faintness typically precludes detailed studies of their nature, and often, even their spectroscopic confirmation. Quasars, on the other hand, are the most luminous non-transient sources known and can be studied in detail at the earliest cosmic epochs. The discovery and characterization of a statistically significant sample of quasars at z>6 is crucial to further study the epoch of reionization, one of the current frontiers of astrophysical research. I will present our efforts on building such a statistical sample, which has led to tripling the number of these quasars in just the last three years. I will discuss the diverse range of properties of this sample, the future direction for distant quasar searches, and also highlight some of the surprises revealed by our current quasar sample as well as our initial follow-up studies from optical to radio wavelengths. In particular, recent observations with ALMA revealed the presence of far-infrared companions around the quasars, and provide key constraints on the properties of the quasar host galaxies. Finally, I will also talk about exciting and encouraging findings from very recent observations.
UDP
Sala de titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
23/10

11:30am
Stuart Ryder
Australian Astronomical Observatory
The Hunt for Companions to Stripped-Envelope Supernovae
The classes of Type IIb, Ib, and Ic core-collapse supernovae appear to represent progressively greater stripping of the progenitor star’s outer envelope prior to explosion, but it is unclear how much of this stripping is due to stellar winds and mass-loss, or to interaction with a massive binary companion. We have used the HST to search for surviving binary companions to nearby stripped-envelope supernovae in the ultraviolet. I will describe our results for the broad-lined Type Ic SN 2002ap, and for the Type IIb SN 2001ig.
UDP
Sala de titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441
Friday
22/11

11:00am
Roberto Decarli
INAF Bologna
The interstellar medium at high redshift
Our understanding of galaxy formation and evolution critically depends on our ability of exposing the properties of the gaseous content of galaxies throughout cosmic history: how much gas is there, in which phase (ionized, atomic, molecular?), in which physical conditions (temperature, density), how efficiently does it turn into stars? We are now entering an exciting era where these questions can be addressed via observations of various gas tracers, especially at mm and sub-mm wavelengths. I will review how to observe various gas phases at high redshift, and discuss lessons we have learned so far from campaigns aimed at characterizing the gas content in galaxies in various cosmic epochs.
UDP
Sala de titulación, Facultad de Ingeniería y Ciencias, Av. Ejército 441