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Astronomy Colloquium

Astronomy Colloquia at Caltech for 2020-2021

Colloquia are held every Wednesday during the academic year at 4pm in the Cahill Hameetman auditorium. Wine and cheese will be served in the Cahill Foyer from 5-5:30pm.

Date Speaker Talk Title
September 30, 2020 Speaker: Di Li Title: The Commensal Radio Astronomy FAST Survey (CRAFTS)
Institute: Chinese Academy of Science
Host: Vikram Ravi Abstract: The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has released its first call for proposal and will be open to the international community next year. Based on a novel technique of high-cadence CAL injection, we have realized the world's first calibrated commensal survey mode, simultaneously taking data for pulsar search, HI galaxies, HI imaging, and FRBs. I introduce here one of the major survey plans, namely, the Commensal Radio Astronomy FAST Survey (CRAFTS, Li et al. 2018), which has discovered more than 100 new pulsars, including a few dozen MSPs, 5 new FRBs, including one new repeater. I will also briefly describe recent FAST results from CRAFTS and other dedicated programs, including new insights into the characteristic energy of FRBs, the formation process of neutron stars, the evolution of interstellar medium, etc.
October, 2, 2020 Speaker: Danielle Berg Title: Extreme UV Emission: Bridging Galaxy Evolution Across Cosmic Time
Institute: OSU / UT Austin
Host: Chuck Steidel Abstract:In the last few years, our first glimpse of the spectral properties of z∼5−7 galaxies has emerged. Deep UV spectra have revealed prominent high-ionization nebular emission lines (i.e., C IV, He II, C III]) indicating that extreme radiation fields may be characteristic of reionization-era systems. While such strong high-ionization emission lines are atypical of the well-studied z∼0−3 galaxy samples, our recent UV spectral campaigns have revealed several galaxies with analogous emission-line features to reionization-era systems. I will discuss the recent detection of extremely strong UV emission in nearby galaxies and the potential sources of their very hard ionizing radiation fields. Such strong detections of high-ionization emission lines have been linked to the leakage of Lyman continuum (LyC) photons (necessary for reionization) both theoretically and observationally. These extreme UV emission-line dwarf galaxies provide a template for the extreme conditions that are important for reionization, however their features are still poorly understood. In preparation for the coming UV window onto the early universe with the advent of ELTs and JWST, I will introduce the COS Legacy Archival Spectroscopic SurveY - an upcoming large HST program designed to disentangle the stellar and nebular spectral signatures of 45 star-forming galaxies. This program will calibrate new UV diagnostics that will allow us to trace galaxy evolution to the distant universe, unveiling the properties of reionization-era galaxies.
October 14, 2020 Speaker: Keith Hawkins Title: Galactic Archaeology with Gaia and Large Spectroscopic Surveys
Institute: UT Austin One of the key objectives of modern astrophysics is to understand the formation and evolution galaxies. In this regard, the Milky Way is a critical testing ground for our theories of galaxy formation. However, dissecting the assembly history of the Galaxy, requires a detailed mapping of the structural, dynamical chemical, and age distributions of its stellar populations. Recently, we have entered an era of large spectroscopic and astrometric surveys, which has begun to pave the way for the exciting advancements in this field. Combining data from the many multi-object spectroscopic surveys, which are already underway, and the rich dataset from Gaia will undoubtedly be the way forward in order to disentangle the full chemo-dynamical history of our Galaxy. In this talk, I will discuss my current work in Galactic archaeology and how large spectroscopic surveys have and can been used to dissect the structure of our Galaxy. I will also explore the future of Galactic archaeology through chemical cartography.
Host: Jim Fuller
October 21, 2020 Speaker: Ben Oppenheimer Title: Why Measuring Black Hole Masses is Essential for Understanding the Circumgalactic Medium
Institute: University of Colorado Abstract: Ripped straight from the headlines of the award of this year's Nobel Prize in Physics, I will begin by discussing the potential connection between a galaxy's central supermassive black hole (SMBH) and its gaseous halo, the circumgalactic medium. Cosmological simulations predict a direct connection between these dramatically different scales, which causally arises from the integrated history of SMBH feedback expelling gas beyond the virial radius. While observing this connection is currently challenging, I will discuss the potential of observing hot gaseous halos in X-rays around Milky Way-mass galaxies. I plan to continue discussing Milky Way-mass halos as observed through via UV absorption line signatures, including changes with redshift from z=3 to today.
Host: Chuck Steidel
October 28, 2020 Speaker: Gwen Rudie
Institute: Carnegie Observatories
Host: Chuck Steidel
November 4, 2020 Speaker: Natasha Batalha
Institute: NASA Ames
Host: Tiffany Meshkat
November 11, 2020 Speaker: Subo Dong
Institute: Peking University
Host: Ilaria Caiasso
November 18, 2020 Speaker: Joss Bland-Hawthorn
Institute: University of Sydney
Host: Chris Martin
December 2, 2020 Speaker: Ann-Marie Madigan
Institute: University of Colorado
Host: Tiffany Meshkat
December 9, 2020 Speaker: Rebecca Jensen-Clem
Institute: UCSC
Host: Mansi Kasliwal
January 6, 2021 Speaker: Ellen Zweibel Title:
Institute: University of Wisconsin-Madison Abstract:
Host: Jim Fullter
January 20, 2021 Speaker: Stephen Smartt Title:
Institute: Queens University Belfast Abstract:
Host: Mansi Kasliwal
January 27, 2021 Speaker: Erin Kara Title:
Institute: MIT Abstract:
Host: Ilaria Caiazzo
February 3, 2021 Speaker: Francois Combes Title:
Institute: Observatoire de Paris Abstract:
Host: Chris Martin
February 10, 2021 Speaker: Silvia Toonen Title:
Institute: University of Birmingham Abstract:
Host: Jim Fuller
February 17, 2021 Speaker: Tim Bedding Title:
Institute: University of Sydney Abstract:
Host: Jim Fuller
March 10, 2021 Speaker: Risa Wechsler (Biard Lecture) Title:
Institute: Stanford University Abstract:
Host: Mansi Kasliwal