Past Events

  • Astronomy seminar: "Accretion in the Shadow of M87"

    David Rittenhouse Laboratory, A2

    Joey Neilsen (Villanova University)

    With the Event Horizon Telescope’s groundbreaking detection of the shadow of the supermassive black hole in M87, we have entered a new era of black hole astrophysics. After presenting the first results from the EHT, I will give a high-energy astrophysicist’s view of what comes next.

  • Astronomy seminar: "Integrated approach to cosmology"

    David Rittenhouse Laboratory, A2

    Andrina Nicola (Princeton/ETH)

    Recent progress in observational cosmology and the establishment of ΛCDM have relied on the combination of different cosmological probes. These probes are not independent, since they all measure the same physical fields. The resulting cross-correlations allow for a robust test of the cosmological model through the consistency of different physical tracers and for the identification of systematics.

  • Astronomy seminar: "Numerical Exercises in Galaxy Formation with Modern Cosmological Hydrodynamical Simulations"

    David Rittenhouse Laboratory, A2

    Shy Genel (Flatiron Institute)

    In the first part of the talk, I will discuss how the new generation of cosmological hydrodynamical simulations can revolutionize our understanding of the origin of galaxy morphologies. In particular, I will present a Lagrangian approach to thinking about galactic angular momentum content and on-going work illuminating relations between galaxy and dark matter halo spins. I will then switch gears and present recent work aiming to quantify chaotic aspects of galaxy evolution using controlled numerical experiments with cosmological simulations.

  • Astronomy seminar: "Primordial Black Holes as Dark Matter Candidates"

    David Rittenhouse Laboratory, A2

    Cristiano Germani (ICC, Barcelona)

    In this talk I will overview the physics of primordial black holes formation from single field inflationary models and discuss their statistical distribution.

  • Astronomy seminar: "The Hercules Stream: stars on Trojan orbits visiting the solar vicinity"

    David Rittenhouse Laboratory, A2

    Elena D’Onghia (University of Wisconsin-Madison)

    The origin of the stars with coherent velocities discovered in the solar neighborhood remains uncertain, but their dynamics and evolution are key to understanding the dynamics of the Galactic stellar disk and ultimately the history of the Milky Way. The Gaia satellite is currently mapping the phase-space of a few million stars in the solar neighborhood. About 350,000 stars within 200 pc of the Sun are identified in streams, bundles of stars that move together in the same direction with a velocity that is distinct from neighboring stars.

  • Astronomy seminar: "Detecting IGM structures in the very early Universe: Status, challenges, and new approaches"

    David Rittenhouse Laboratory, A2

    Nithya Thyagarajan (NRAO)

    Direct detection of evolving neutral Hydrogen structures from the Cosmic Dawn and Reionization Epochs (EoR) will reveal the nature of the first stars and galaxies as well as complete our understanding of a significant evolutionary phase of the Universe. In contrast with some recent exciting results from the EDGES experiment, detection of IGM structures using redshifted 21 cm by many experiments such as the MWA, LOFAR, and PAPER that commenced in the last decade has remained elusive.

  • Astronomy seminar: "Dark Matter in Disequilibrium"

    David Rittenhouse Laboratory, A2

    Mariangela Lisanti, Princeton University

    The Gaia mission is in the process of mapping nearly 1% of the Milky Way’s stars. This data set is unprecedented and provides a unique view into the formation history of our Galaxy and its associated dark matter halo. I will review results based on the most recent Gaia data release, which demonstrate that the inner Galaxy is dominated by the stellar remnants of a single massive satellite galaxy that merged with the Milky Way early on.

  • Astronomy seminar: "Distances for Cosmology"

    David Rittenhouse Laboratory, A2

    Rachael Beaton, Princeton/Carnegie

    Distances are the fundamental datum by which we translate observational quantities into astrophysical ones and distances remain difficult to measure. I will describe techniques that use old stellar populations in galaxies to determine distances because old stellar populations exist in all galaxies of all hubble types, in each structural component of a galaxy, and are observable regardless of the galaxy's orientation. Thus, old stellar populations provide a means of reaching galaxies and galaxy structures that are not feasible via the classical Cepheid-based distance ladder.

  • Astronomy seminar: "Using the environment to infer supernova progenitor properties"

    David Rittenhouse Laboratory, A6

    Lluis Galbany, University of Pittsburgh

    Integral Field Spectroscopy (IFS) applied to supernova (SN) environmental studies have shown the potential of this technique to directly characterize the galactic environmental parameters at SN locations, compare them to those at different locations of the galaxy, and put constraints on progenitor stars for different SN types. In this talk, I will summarize current efforts from the PISCO compilation, Hi-KIDS, MaNGA, and the AMUSING surveys, that have put together more than 500 SN hosts observed with IFS, and give details about published results from these datasets. 

  • Special Seminar: "This Is Not A Diversity Talk" - POSTPONED MAKE UP DATE TBD

    David Rittenhouse Laboratory, A8

    John A. Johnson, The Harvard-Smithsonian Center for Astrophysics

    The American discourse on the various disparities present in society generally, and academia specifically, focuses primarily on observations of the state of a given situation---e.g. a lack of diversity---rather than on the actions that lead to such a state. This approach is just as dissatisfying and ultimately ineffectual as observing that certain stars are "bright," rather than describing any of the physical principles that lead to the observed properties of a star.