ASD Colloquium Series - Fall 2019

ASD Colloquium Series - Fall 2019

The Astrophysics Science Division colloquia occur on Tuesdays at 3:45 pm, with an opportunity to meet the speaker at 3:30 pm, in building 34, room W150 (unless otherwise noted). Schedules from past colloquium seasons are available.

Contact: Knicole Colon


Aug 27 Special Location: Building 34, Room W120A/B
Charlie Conroy (Harvard University) - Assembling our Galaxy


Sep 03 No Colloquium
Sep 10 Marcelle Soares-Santos (Brandeis University) - Cosmology in the era of multi-messenger astronomy with gravitational waves
Sep 17 Special Location: Building 34, Room W120A/B
Jessica Werk (University of Washington) - A Colossal Galaxy Adventure
Sep 24 Matteo Cantiello (Flatiron Institute) - The New Era of Stellar Physics


Oct 01 Cara Battersby (University of Connecticut) - The Milky Way Laboratory
Oct 08 Special Location: Building 34, Room W120B
Davide Lazzati (Oregon State University) - Electromagnetic emission from binary neutron star mergers
Oct 15 Kirsten Hall (Johns Hopkins University)
Oct 22 No Colloquium
Oct 29 Special Location: Building 34, Room W305
Jessie Christiansen (NASA Exoplanet Science Institute)


Nov 05 Special Location: Building 3 Auditorium
Erika Hamden (University of Arizona)
Nov 12 Kari Frank (Northwestern University)
Nov 19 Stephen Taylor (Caltech)
Nov 26 No Colloquium - Thanksgiving Week


Dec 03 Ryan Trainor (Franklin and Marshall College)
Dec 10 Michele Trenti (University of Melbourne)

Assembling our Galaxy

Charlie Conroy

Harvard University

Tuesday, Aug 27, 2019


I will review ongoing work aimed at understanding when and how the major structural components of our Galaxy came into place. The combination of Gaia DR2 and spectroscopic data has revealed that the stellar halo contains a remarkable degree of structure, and appears to have formed partially by dynamical processes within the disk, and partially from accreted dwarf galaxies. Our simulations of the stellar disk predict that the clustered nature of star formation imprints a high degree of structure in phase+chemistry space. This structure is now being measured in the data, and promises to deliver new insights into the nature of star formation and the dynamical history of the disk.

Cosmology in the era of multi-messenger astronomy with gravitational waves

Marcelle Soares-Santos

Brandeis University

Tuesday, Sep 10, 2019


Motivated by the exciting prospect of a new wealth of information arising from the first observations of gravitational and electromagnetic radiation from the same astrophysical phenomena, the Dark Energy Survey (DES) has established a search and discovery program for the optical transients associated with LIGO/Virgo events (DESGW). Using the Dark Energy Camera (DECam), DESGW has contributed to the discovery of the optical transient associated with the neutron star merger GW170817, and produced the first cosmological measurements using gravitational wave events as standard sirens. We now pursue new results during the third, and ongoing, observing campaign. In this talk, I present an overview of our results, and discuss its implications for the emerging field of multi-messenger cosmology with gravitational waves and optical data.

A Colossal Galaxy Adventure

Jessica Werk

University of Washington

Tuesday, Sep 17, 2019


Most of the atomic matter in the Universe courses through the dark, vast spaces between galaxies. This diffuse gas cycles into and out of galaxies multiple times. It will form new stars and become swept up in violent stellar end-of-life processes. Astronomers believe that this gaseous cycle lies at the heart of galaxy evolution. Yet, it has been difficult to observe directly. Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of the Cosmic Origins Spectrograph on the Hubble Space Telescope, observations and simulations of this diffuse material have emerged at the frontier of galaxy evolution studies. In the last decade, we have learned that Milky Way mass galaxies harbor enough material outside of their visible disks to sustain star-formation for billions of years. Remarkably, our observations indicate that most of the heavy elements on earth cycled back and forth multiple times through the Milky Way’s extended halo before the formation of the solar system. In the spirit of MS-DOS adventure games, I have designed a fully interactive colloquium that operates on a complex network of powerpoint hyperlinks. In this adventure, you will choose any of 36 possible tracks on which to explore observational and simulated signatures of cosmic gas flows.

The New Era of Stellar Physics

Matteo Cantiello

Flatiron Institute

Tuesday, Sep 24, 2019


Stellar astrophysics is undergoing a renaissance driven by new observational and theoretical capabilities. Wide-field time-domain surveys have uncovered new classes of stellar explosions, helping to understand how stars evolve and end their lives. Gravitational-wave astronomy is providing exciting insights in the properties of the final remnants of massive stars. Asteroseismology, the study of waves in stars, is also producing dramatic breakthroughs in stellar structure and evolution. Thanks to space astrometry, accurate distances are now available for an unprecedented number of galactic stars.

From the theoretical standpoint, it is increasingly possible to study aspects of the three-dimensional structure of stars using targeted numerical simulations. These studies can then be used to develop more accurate models of these physics in one-dimensional stellar evolution codes. I will review some of the most important results in stellar physics of the last few years, and highlight what are the most relevant puzzles that still need to be solved. I will put particular emphasis on the physics of massive stars, which are the progenitors of core-collapse supernovae, gamma-ray bursts and the massive compact remnants observed by LIGO.

Electromagnetic emission from binary neutron star mergers

Davide Lazzati

Oregon State University

Tuesday, Oct 08, 2019


The detection of gravitational waves, gamma-rays, and multi wavelength radiation from the binary neutron star merger GW170817 has been an enormous breakthrough in astrophysics. It has confirmed some theoretical expectations and opened new riddles. I will extensively introduce the observations and physics of the event and then concentrate on the non-thermal component of the emission and on the possible the association of binary neutron star mergers with short-duration gamma-ray bursts. I will show that the most likely scenario is the one in which GW170817 produced a canonical short gamma-ray burst jet that was misaligned with our line of sight, resulting in unusual behavior. I will finally discuss the results of the O3 observation period of LIGO and what to expect from the future.

The Milky Way Laboratory

Cara Battersby

University of Connecticut

Tuesday, Oct 01, 2019


Our own Milky Way Galaxy is a powerful and relatively nearby laboratory in which to study the physical processes that occur throughout the Universe. From the organization of gas on galactic scales to the life cycle of gas and stars under varied environmental conditions, studies of our Milky Way underpin many areas of modern astrophysics. I will present a brief tour of our Milky Way Laboratory, including 1) the connection between long, filamentary molecular clouds and spiral structure, and 2) how observing our extreme, turbulent Galactic Center (the Central Molecular Zone) can help us learn more about how gas is converted into stars during the peak epoch of cosmic star formation. I will also briefly discuss the Origins Space Telescope, a NASA mission concept study for the 2020 Decadal survey, opening up about 3 orders of magnitude of discovery space on science from first stars to life.

Past Colloqia Schedules

2019: Fall, Spring
2018: Fall, Spring
2017: Fall, Spring
2016: Fall, Spring
2015: Fall, Spring
2014: Fall, Spring
2013: Fall, Spring, Summer
2012: Fall, Spring
2011: Fall, Spring
2010: Fall, Spring

NASA Logo, National Aeronautics and Space Administration