Past Events

  • 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.

  • Astronomy seminar: "Measurements of Degree-Scale B-mode Polarization with the BICEP/Keck Experiments at South Pole"

    David Rittehouse Laboratory, A6

    Benjamin Racine, Harvard-Smithsonian Center for Astrophysics

    The BICEP and Keck experiments, located at the South Pole, are currently observing the polarized microwave sky at the degree scale using refractive telescopes. They are searching for a signature of primordial gravitational waves in the so-called B modes of the cosmic microwave background (CMB), parametrized with the tensor-to-scalar ratio r. In this talk I will introduce our latest analysis which includes BICEP2 and Keck array data up to the end of 2015.

  • Astronomy seminar: "TBA"

    David Rittenhouse Laboratory, A6

    Barth Netterfield, University of Toronto

  • Astronomy seminar: "The Hunt for Exomoons"

    David Rittenhouse Laboratory, A6

    David Kipping, Columbia University

    Since astronomers first started detecting exoplanets, interest in possible exomoons soon followed. Moons could be habitable worlds in their own right but also influence the habitability of planets they orbit. Besides from habitability, discovering moons would provide rich insights into the formation and evolution of planetary systems, potentially revealing the banality/uniqueness of our own solar system’s architecture.

  • Astronomy seminar: "Reverse Engineering the local Universe"

    David Rittenhouse Laboratory

    Edoardo Carlesi, IAP Potsdam

    Constrained simulations (CS) provide a powerful alternative approach to the random-phase Initial Conditions (ICs) cosmological simulations. In this method, galaxy peculiar velocity measurements are used to reconstruct the matter density field and generate a set of ICs whose final outcome closely matches the observed Universe. Hence, while the results obtained with the standard techniques can be compared to the data in a statistical sense only, in a CS we can exploit the constraining potential of the high-precision near-field observations by means of a direct comparison. 

  • Astronomy seminar: "Stellar Forensics with the Most Powerful Explosions in the Universe"

    David Rittenhouse Laboratory, A6

    Maryam Modjaz, New York University

    Supernovae (SNe) and Long-duration Gamma-ray Bursts (GRBs) are exploding stars and constitute the most powerful explosions in the universe. Since they are visible over large cosmological distances, release elements heavier than Helium, and leave behind extreme remnants such as black holes, they are fascinating objects, as well as crucial tools for many areas of astrophysics, including cosmology.