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Astrophysics Seminars From 2021 - 2022

Contents


Fall 2021


October 1, 2021

NOTE: CASS All-Hands Meet & Greet @ 3:00PM
 CASS Welcome event led by George Fuller

Zoom link


 Meeting ID: 932 0300 1150

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Meeting ID: 932 0300 1150
Find your local number: https://ucsd.zoom.us/u/aydAfQdjx


We are reserving our first CASS Seminar slot, Friday, October 1, 3:00 PM, for a general meet-and-greet. We will conduct this remotely (via Zoom). I encourage all of those associated with, or interested in, CASS, from any Department at UCSD or SDSU, to attend. I especially encourage new students and postdocs to attend. We will introduce ourselves and say (in a sentence or two!) what our interests are in the grand astrophysics enterprise, from elementary particle physics to biochemistry.



October 8, 2021

 "Black Holes, Galaxies, and the Evolution of the Universe"

Meg Urry
Professor
Yale University
https://ucsd.zoom.us/j/97425912411?pwd=cGczbWhzUTh4ZjMreUxURzJZQk5SQT09


 Meeting ID: 974 2591 2411
Password: 871087

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Meeting ID: 974 2591 2411
Find your local number: https://ucsd.zoom.us/u/ahUiL8211

ABSTRACT: Black holes form at the centers of galaxies in the young Universe and, over the next 13 billion years, they grow together by factors of a million or more in mass. This growth generates energy that can affect galaxy evolution, including that of the Milky Way galaxy in which we live. In this talk, I describe how recent “wedding cake” X-ray+infrared+ optical surveys of the sky have led to a quantitative description of black hole growth over the last ~12 billion years. Most Active Galactic Nuclei are heavily obscured and thus look like inactive galaxies in optical surveys, so our census effectively quadruples the amount of accretion, and thus the amount of energy deposited in AGN host galaxies. However, contrary to leading models, our data suggest that for only a minority of galaxies does merger-triggered AGN “feedback” cause rapid quenching of star formation.



October 15, 2021

 "Revealing dark matter with strongly lensed quasars"

Anna Nierenberg
Assistant Professor
UC Merced
https://ucsd.zoom.us/j/97765100998?pwd=ZVVzbW5ZL1g2NGtWeGpYM0FmVmVyUT09


 Meeting ID: 977 6510 0998
Password: 834402

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Meeting ID: 977 6510 0998

Find your local number:
https://ucsd.zoom.us/u/aIW6pwu0E

ABSTRACT: The shapes and abundance of dark matter halos are directly tied to the fundamental physics of dark matter particles such as its free streaming-length and self-interaction cross section, and have thus proven to be essential probes of this otherwise elusive form of matter. Traditional measurements of the shapes and abundance of dark matter halos rely on observations of stars and galaxies which form within them. Such measurements become difficult at low halo masses, as galaxy formation becomes increasingly suppressed. Thus tests of dark matter at low halo-mass scales require a tracer which does not rely on the presence of stars. We have shown that strong gravitational narrow-line lensing provides a powerful probe of the presence of low mass structure in a much larger sample of systems than was previously possible, and enables the detection of dark matter halos well into the regime where the majority of halos are expected to be dark. I will present our results placing limits on a turnover in the halo mass function and measuring the low-mass end of the halo-mass concentration relation. I will also describe our upcoming JWST program to measure cold-torus flux ratios, and conclude by looking to the future for the next generation of instruments, telescopes, and surveys which will enable us to expand the narrow-line method to an order of magnitude larger sample.



October 22, 2021

 "Opening the Infrared Treasure Chest with JWST"

John Mather
Senior Astrophysicist
NASA/Goddard
https://ucsd.zoom.us/j/93092340612?pwd=SUhINi9FOG0wYnBwUXFtM2Y4MTRaQT09


 Meeting ID: 930 9234 0612
Password: 963869

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Meeting ID: 930 9234 0612
Find your local number: https://ucsd.zoom.us/u/ac2WWeSjcg

ABSTRACT: The long-awaited James Webb Space Telescope is planned for launch on Dec. 18, 2021. With its 6.5 m deployable primary mirror, and cameras and spectrometers covering 0.6 to 28 µm, it promises extraordinary improvements in observing capabilities. Webb will be able to observe the first objects that formed after the Big Bang, the growth of galaxies, the formation of stars and planetary systems, individual exoplanets through coronography and transit spectroscopy, and all objects in the Solar System from Mars on out. It could observe a 1 cm2 bumblebee at the distance of the Moon, in reflected sunlight and thermal emission. I will review the observatory capabilities and planned observing program, and illustrate the history of the concept from 1988 to now. The Webb is a joint project of NASA with the European and Canadian space agencies.



October 29, 2021

 "Gravitational-wave multimessenger astrophysics from the production of gold to the expansion of the Universe"

Hsin-Yu Chen
NASA Einstein Fellow
MIT
https://ucsd.zoom.us/j/95150721516?pwd=ZDNZRm1vMTVRNUNTWnFzdnYyQVREUT09


 Meeting ID: 951 5072 1516
Password: 167826

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Meeting ID: 951 5072 1516
Find your local number: https://ucsd.zoom.us/u/aL34DVC4K

ABSTRACT: Over last six years, the LIGO-Virgo detections of gravitational waves from compact binary mergers have underlined their promise as an independent and powerful tool to explore the Universe. Nevertheless, the electromagnetic observation of the counterparts of GW sources provides different and complementary information about the binary systems, and therefore the combination of `multimessengers' is expected to lead to significantly enhanced science outcomes. In this talk, I will discuss what we learned in cosmology, nuclear physics, and heavy-elements production from LIGO-Virgo observations. I will then discuss the future aspects and challenges in these areas.



November 5, 2021

Kareem El-Badry
Postdoctoral Fellow
Harvard CfA



November 12, 2021

Ting-Wen Lan
Assistant Professor
National Taiwan University



November 19, 2021

Eugene Chiang
Professor
UC Berkeley



November 26, 2021

NOTE: No Seminar - Thanksgiving holiday



December 3, 2021

 "Space Observatories for Ultrahigh Energy Astroparticles"

Angela Olinto
Professor
University of Chicago


 ABSTRACT: What are the mysterious sources of the most energetic particles ever observed? What astrophysical sources produce very energetic neutrinos? How do particles interact at extreme energies? Building on the progress achieved by the ground-based observations we are developing space and sub-orbital missions to answer these questions. The Extreme Universe Space Observatory (EUSO) on a super pressure balloon (SPB) is designed to detect ultrahigh energy astroparticles from above. EUSO-SPB1 flew in 2017 with a fluorescence telescope. EUSO-SPB2 is being built to observe both fluorescence and Cherenkov from ultrahigh energy cosmic rays (UHECRs) and neutrinos. These sub-orbital missions lead to POEMMA, the Probe Of Extreme Multi-Messenger Astrophysics, a space mission designed to discover the sources of UHECRs and to observe neutrinos above 20 PeV from energetic transient events. POEMMA will open new Multi-Messenger windows onto the most energetic events in the Universe, enabling the study of new astrophysics and particle physics at these extreme energies.