2018 UDP Seminar Series
♦ October 19, 2PM: Carnegie and Las Campanas Observatory; science and instrumentation highlights
Leopoldo Infante (Carnegies)
Room: Sala Titulacion, Facultad Ingenieria y Ciencias, UDP
In this talk, I will give a brief description of the role played by the Carnegie Institution for Science (former Carnegie Institution of Washington) in the history of astronomy during the last century and the need to establish an observatory in the southern hemisphere at the end 1960, which became Las Campanas Observatory. I will discuss the current and future availability of telescopes and instrumentation in LCO, as well as the most recent scientific discoveries made in LCO and the opportunities that open up for the Chilean astronomical community.
♦ October 26, 3PM
Stefano Bovino (Universidad de Concepción)
♦ November 9, 3PM (joint UDP-UNAB)
Claudia Paladini (ESO) – Location: UNAB
♦ November 16, 3PM
Tanio Diaz (UDP)
♦ November 23, 3PM
Ghina Halabi (Institute of Astronomy, University of Cambridge)
♦ December 7, 3PM (joint UDP-UNAB)
Nicolas Tejos (PUC-V)
♦ December 18, 3PM
Kohei Ichikawa (Columbia University, USA; Tohoku University, Japan)
For other talks in Santiago see the SOCHIAS calender
♦ October 11, 2PM
Jhon Yana Galarza (IAG, USP Brazil): The effect of stellar activity on the stellar parameters of a young solar twin
Most spectroscopic surveys of stellar chemical composition assume that spectroscopic
equilibrium holds in solar-type stars, even for young spotted stars with high stellar activity.
However, it is known that there are important abundance anomalies in young open clusters,
which could be related to overexcitation and overionization effects, hence potentially affecting
the assumption of spectroscopic equilibrium. Furthermore, it is known that magnetic activity
causes radial velocity variability, hampering true detection of exoplanets.
In this work, we have tested for the first time variations in stellar parameters and chemical
abundances for the young solar twin HIP36515 (~0.6 Gyr, Prot ~ 5 days). This object has stellar
parameters well established and its activity cycle is estimated in ~7 years (from our previous
observations with HARPS at LaSilla/ESO). The stellar parameters of three different epochs in
the cycle (minimum, intermediate and maximum) were estimated using spectroscopic
equilibrium, achieving an extremely high precision (~5 K in effective temperature, ~0.01 dex in
surface gravity and metallicity). Surprisingly, we find a correlation between effective
temperature (-0.85, p-value=0.18) and microturbulence (+0.98, p-value=0.02) with stellar
♦October 5, 3PM (joint UDP-UNAB )
Laura Perez (U. Chile): The Role of Substructures in Protoplanetary Disks
During their formation, young pre-main sequence stars are generally surrounded by a gaseous accretion disk, which provides a large reservoir of material available for the eventual formation of planets. This process will leave an imprint on the distribution of solid particles at different locations in the disk, resulting in a variety of substructure (e.g. gaps, rings, spirals, vortices) over large and small scales. The role of these small-scale features is fundamental: theory predicts that without substructure large solids would be lost due to radial drift, impeding planetesimal and planet formation. In this talk, I will discuss results from our ALMA Large Program aimed at characterizing the underlying substructure of classical disks with superb spatial resolution, down to a radius of few au. I will introduce the main survey results and discuss our work in a misaligned disk system as well as in binary/multiple systems.
♦ October 1, 3PM
Rebecca McElroy (MPIA): Active galaxies in the local universe: triggering, variability, and feedback
This talk aims to investigate three important phenomena in the study of active galactic nuclei: how AGN are triggered, how they vary throughout their lifetimes, and how they can effect their host galaxies through feedback.
We search for evidence of triggering by mergers using MUSE-VLT data from the Close AGN Reference Survey (CARS). We compare stellar kinematics of our active galaxies and a comparison sample of inactive galaxies to measure the deviation from disk like rotation. We show that the AGN have a slight enhancement in large scale asymmetry. Many AGN are known to vary strongly throughout their lifetime. We observed known changing look AGN Mrk 1018 as part of CARS and found that the broad lines and continuum emission had dramatically changed for a second time. We attempt to explain the possible causes for this recent change, and discuss what such short timescale variability means for theories of AGN feedback. Finally, we show that outflows are prevalent in luminous local type 2 AGN using multiple component Gaussian emission line modelling to disentangle the kinematic and ionisation properties of emission lines. This allows us to show that shock-like emission is present in these galaxies, demonstrating that the outflows are directly impacting the surrounding ISM within the galaxies.
♦ September 28, 3PM
Julio Carballo-Bello (PUC): Globular clusters and the hierarchical formation of the Milky Way
Globular clusters have played an important role in the study of the processes that led to the formation of our Galaxy. Moreover, the dual Galactic globular cluster system is considered a manifestation of its hierarchical formation in the context of the Lambda-CDM scenario. Wide-field imaging and spectroscopy, as the ones obtained for our project, are crucial tools to unveil the remnants of their progenitor dwarf galaxies, already assimilated by the Milky Way. In this talk, I will present some of the results obtained in this long-term project, proving that globular clusters are still useful relics in the field of Near-Field cosmology.
♦ September 14, 11AM (special seminar)
Demian Arancibia (ASTROdata):Astroinformatics Program – Chile: An example initiative using astronomy for economic development in Chile
The Astroinformatics Program is funded by the Ministry of Economy. Its mission is to identify and initiate measures and investments to diversify and grow Chilean digital economy, using our natural resources for Astronomy and the field data-driven challenges. According to the strategy of CORFO, the capacity to add data-driven value will be critical for competitive edges across industries over next decade, and a driver for diversification of the Chilean productive matrix. We worked with scientific and industrial communities to facilitate multi-sector agreements about what are our opportunities to achieve this mission. In our first year of work, we produced a high-level system concept that is potentially fit for increasing Chilean protagonism in Astronomy, digital capacity development, technology transfer and is sustainable from an economic point of view. This presentation is a progress report and an invitation to collaborate in the next steps of implementation.
♦ September 7, 3PM (joint UDP-UNAB)
George Privon (U. Florida): Star Formation and Nuclear Activity: Dwarfs to ULIRGs
The stellar mass of star forming galaxies is thought to increase in a quasi-steady state, where the rate depends on the gas fraction and star formation efficiency. Galaxy mergers can lead to more rapid growth while active galactic nuclei have been argued to play an important role in halting star formation. These processes are tied together through the multiphase interstellar medium. I will discuss a program exploring so-called “dense gas” tracers, the use of dust emission as a probe of total molecular gas mass, and the behavior of starbursts in merging dwarf galaxies. This use of multiwavelength tracers and hydrodynamic simulations probes galaxy evolution along axes of nuclear activity, redshift, gas fraction, and metallicity. From these studies I will show new results on identification of heavily obscured AGN and intriguing differences in how mergers trigger starbursts in high gas fraction systems.
♦ August 31, 3PM
Ezequiel Treister (PUC): Physical Properties of the Gas in the Nuclear Regions of Nearby Dual AGN
Major galaxy mergers hosting two supermassive black holes (SMBHs) actively growing separated by less than 10 kpc, the so-called dual active galactic nuclei (AGNs) are ideal targets for understanding SMBH feeding, obscuration, and testing unification models and galaxy evolution. In this talk, I will present the main results from our program aimed to obtain optical and near-IR Integral Field Unit (IFU) spectroscopy and ALMA maps for a sample of confirmed nearby dual AGN. In addition to providing general properties of this population, I will focus on two remarkable systems, NGC6240 and Mrk 463.
At a distance of 210 Mpc, and a nuclear separation of ∼4 kpc, Mrk 463 is an excellent laboratory to study the gas dynamics, star formation processes and SMBH accretion in a late-stage gas-rich major galaxy merger. The optical data, which map the full extent of the merger, show evidence for a biconical outflow and material outflowing at >600 km/s, both associated with the east nucleus, along with large-scale gradients likely related to the ongoing galaxy merger. The ALMA observations of 12CO(2–1) and adjacent 1 mm continuum reveal the presence of ~1e9Mo in molecular gas in the system. The molecular gas shows velocity gradients of ~800 km/s and ~400 km/s around the Mrk 463E and 463W nuclei, respectively. We conclude that, in this system, the infall of ∼100s Mo/yr of molecular gas is in rough balance with the removal of ionized gas by a biconical outflow being fueled by a relatively small, <0.01% of accretion onto each SMBH.
We will further present the highest resolution maps of the merging galaxy system NGC6240, which hosts two SMBH growing simultaneously. At 0.03″ (15 pc), the ALMA 12CO(2-1) observations are a perfect match for existing Hubble optical and near-IR observations of this system. We find that most of the molecular gas is found in between the two nuclei but forming a clumpy stream and not a smooth rotating disk as it was previously assumed based on lower resolution data. A clear velocity gradient suggests that the molecular gas is getting ready for the next stage, in which will coalesce around each nuclei, being available significantly increase the amount of accretion onto each SMBH. We further detect the presence of significant high velocity, >500 km/s, outflows, responsible for the removal of a fraction of the material.
These results clearly show the importance of performing high resolution multi wavelength studies covering pc to kpc scales in order to understand the complex connection between black hole growth and galaxy evolution in this critical phase.
♦ August 17, 3PM at UDP
Stephane Blondin (CNRS, UMI-LFCA, PUC): Predicting the radiative display of Type Ia Supernovae: The case for multiple progenitor channels
Type Ia supernovae (SNe Ia) are amongst the most energetic stellar explosions. With typical luminosities several billion times that of the Sun, SNe Ia are visible across a large fraction of the observable universe, and enabled the discovery of its accelerated expansion. These events are thought to result from the thermonuclear disruption of a carbon-oxygen white dwarf (WD) star as it approaches the Chandrasekhar-mass limit, through accretion from a binary companion. However, the nature of this companion and the mechanisms by which the WD explodes are still debated. I will present the numerical setup developed with my collaborators to predict the light curves and spectra of SNe Ia, which provide support to the viability of the standard Chandrasekhar-mass model for most events. However, this standard model is difficult to reconcile with low-luminosity SNe Ia, making a strong case for the existence of multiple progenitor channels for these events.