Joint IAS Princeton University Astrophysics Colloquium 

2021 Spring Colloquium Series

The Spring 2021 Joint Astrophysics Colloquium will be held virtually on Tuesdays at 11AM and will be and will be followed by the Bahcall Lunch at 12:30, also virtual.

Date   Name    Talk (video link)
Feb. 2, 2021 Eliot Quataert
The Impact of Cosmic-Rays on Galaxy Formation
Relativistic cosmic-rays created by stellar and black hole feedback may play an important role in many aspects of structure formation.  Cosmic-rays can drive outflows from star forming galaxies and heat diffuse gas in the circumgalactic and intergalactic medium.  In this talk I will describe some of the possible impact(s) of cosmic-rays on galaxy formation, observational probes of their impact, and the
theortical uncertainities in our understanding of the role of cosmic rays in structure formation.                                   
Feb. 9, 2021 Feryal Özel
University of Arizona
Black Hole Physics at the Horizon Scale
Recent observational advances with the Event Horizon Telescope, GRAVITY, and LIGO/VIRGO have opened up new avenues for studying black hole physics at horizon scales. In this talk, I will discuss what we have learned about the spacetimes of astrophysical black holes and how strong-field gravity is imprinted on their images. I will also present how the observations help us model and understand the heating and acceleration of plasmas on horizon scales.
Feb. 16, 2021 Sherry Suyu
Max Planck Institute for Astrophysics
Cosmology with Gravitational Lens Time Delays
Strong gravitational lenses with measured time delays between the multiple images can be used to determine the Hubble constant (H0) that sets the expansion rate of the Universe. An independent determination of H0 is important to ascertain the possible need of new physics beyond the standard cosmological model, given the tension in current H0 measurements. I will describe techniques for measuring H0 from lensing with a realistic account of systematic uncertainties, and present the latest results from a program aimed to measure H0 from lensing. Search is underway to find new lenses in imaging surveys. An exciting discovery of the first strongly lensed supernova offered a rare opportunity to perform a true blind test of our modeling techniques. I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe.
Feb. 23, 2021 Jørgen Christensen-Dalsgaard
Aarhus University
Probing red giants with Kepler
The frequencies of oscillations observed on a stellar surface carry information about the properties of the stellar interior. Asteroseismology, i.e., the unravelling of this information, has made a huge leap thanks to the photometric observations obtained with NASA' Kepler mission, launched in 2009 to search for planets around other stars. In my talk I focus on the study of red-giant stars, showing a broad range of oscillations, probing both the outer parts and the deep core of the stars. Amongst other remarkable results, this has allowed distinguishing stars according to their nuclear energy source and provided detailed information about the properties of internal rotation in these late stages of stellar evolution.
Mar. 2, 2021
Jennifer van Saders
University of Hawaii
Making Sense of Stellar Rotation in Low Mass Stars
Stellar rotation carries a wealth of information about stellar populations. In particular, the technique of gyrochronology was developed to utilize the spin-down of stars as a function of time as an indicator of stellar age. Gyrochronology has the potential to yield precise ages for large samples of stars, providing unprecedented chronological information for studies of the Milky Way and extrasolar planets. However, the technique is in its adolescence: it has been tested and validated under limited scenarios, but its weaknesses and limitations have hitherto been largely unexplored. With time-domain data we can address these gaps: we now have access to datasets of rotation periods for tens of thousands of stars, as well as independent asteroseismic ages and rotation periods for a few hundred old (main sequence) stars.  I will discuss my comparisons of theoretical rotation models to these data, which have yielded unexpected insights into the rotational and magnetic lives of stars (and the Sun!), as well as a better understanding of the power and peril of gyrochronology as a tool. 
Mar. 16, 2021 Brian Nord
University of Chicago / Fermilab
Mar. 23, 2021 Julia Roman-Duval
Space Telescope Science Institute
The Nearby Universe  -  A Laboratory to Study the Cosmic Build-up
of Dust and Metals in Galaxies

A key component of the baryon cycle in galaxies is the cycle of metals between the gas and the dust phases in the neutral interstellar medium (ISM). How this cycle depends on environment (in particular metallicity and density) has important implications for how accurately we can trace the chemical enrichment of the universe over cosmic times; either by using dust emission in the far-infrared as a tracer of the ISM in galaxies at high and low redshift; or by using spectroscopy of damped Lyman-alpha systems (DLAs) to measure chemical abundances in neutral gas over a wide range of redshifts. Variations of the abundance and properties of dust within and between galaxies furthermore profoundly affects their evolution, given the key role that dust plays in the chemistry, radiative transfer, and thermodynamics of galaxies. In this talk, I will present results from several independent observational efforts to characterize the dust abundance (dust-to-gas and dust-to-metal ratios) in the Magellanic Clouds and other nearby low-metallicity galaxies, using emission-based tracers of the interstellar medium (FIR, HI 21 cm, CO rotational emission) to map their dust and gas content on the one hand; and using UV absorption spectroscopy with Hubble to directly count metals in the gas phase on the other hand. Both types of studies demonstrate significant variations of the dust abundance with density (within galaxies) and metallicity (between galaxies), which have important implications for the sub-grid physics of galaxy evolution. Surprising patterns in the gas-phase abundances were found from the Hubble spectroscopy, and an interesting tension between the emission-based and absorption-based measurements remains unexplained.
Mar. 30, 2021 Anna Watts
University of Amsterdam
Apr. 6, 2021 Zhaohuan Zhu
University of Nevada, Las Vegas
Apr. 13, 2021 Yamila Miguel
Leiden Observatory
Apr. 20, 2021 Ignas Snellen
Leiden Observatory
Apr. 27, 2021 Alberto Bolatto
University of Maryland

2020 Fall Colloquium Series

The Fall 2020 Joint Astrophysics Colloquium will be held virtually on Tuesdays at 11AM and will be followed by the Bahcall Lunch at 12:30, also virtual.  Please find the Fall speaker schedule here.

Videos on IAS website:

2020 Summer Colloquium Series

The 2020 Summer Colloquium Series led by Professor Jenny Greene has concluded. The list of speakers, talk titles and select colloquium recording links appear below. 

Date   Name    Talk
Jun 30, 2020 Evan Schneider The Origin of Multiphase Galaxy Outflows
July  7, 2020 Courtney Dressing Exploring Planets Orbiting Nearby Stars
July 14, 2020 Geraldine Cochran Promoting Diversity and Addressing Barriers in Physics
July 21, 2020 Sean Johnson Observations of the gas flows that govern galaxy evolution in absorption and emission at z<1
July 28, 2020 Julie Posselt Equity in Science: Representation, Culture, and the Dynamics of Change in Graduate Education
Aug  4, 2020 Richard Anantua A Glimpse into Horizon-Scale Physics Using Movies and Polarization Maps
Aug 11, 2020 Casey Miller Practicing Equity in Graduate Admission
Aug 25, 2020 Kareem El-Badry Emission-line stars, binary mass transfer, and the search for detached stellar mass black hole