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ASD Colloquium Series - Spring 2021

ASD Colloquium Series - Spring 2021

The Astrophysics Science Division colloquia occur virtuallly on Tuesdays at 3:45 pm. Schedules from past colloquium seasons are available.

Contact: Knicole Colon

January

Jan 05 No Colloquium - Week of Winter AAS Workshops
Jan 12 No Colloquium - Week of Winter AAS Meeting
Jan 19 No Colloquium - MLK Day Weekend, Inauguration Week
Jan 26 Virtual Colloquium
Richard Anantua (Center for Astrophysics | Harvard & Smithsonian, Flatiron Institute - Center for Computational Astrophysics, Event Horizon Telescope) - A Glimpse into EHT-Scale Physics Using Movies and Polarization Maps

February

Feb 02 No Colloquium
Feb 09 Virtual Colloquium
Naoko Kurahashi Neilson (Drexel University) - Experimental Neutrino Astrophysics and the Need for a Future Gamma-ray Observatory
Feb 16 No Colloquium - President's Day Weekend
Feb 23 Virtual Colloquium
Kate Grier (University of Arizona) - Quasars and Supermassive Black Holes: Uncovering Mysteries with Variability and Reverberation Mapping

March

Mar 02 No Colloquium
Mar 09 No Colloquium
Mar 16 Virtual Colloquium
Louise Edwards (California Polytechnic State University)
Mar 23 Virtual Colloquium
Jason Rowe (Bishop's University)
Mar 30 Virtual Colloquium
Jessica Gaskin (NASA MSFC)

April

Apr 06 Virtual Colloquium - Easter Weekend
Carl Fields (Michigan State University, Arizona State University
Apr 13 Virtual Colloquium
Monica Colpi (INFN Milano)
Apr 20 Virtual Colloquium
Anne Jaskot (Williams College)
Apr 27 Virtual Colloquium
Jeff Fillipini (University of Illinois at Urbana-Champaign)

May

May 04 Virtual Colloquium
Enrico Ramirez-Ruiz (UC Santa Cruz)
May 11 Virtual Colloquium
Marcel Agueros (Columbia University)
May 18 Virtual Colloquium
Andra Stroe (Center for Astrophysics | Harvard & Smithsonian)
May 25 Virtual Colloquium
Antonija Oklopčić (University of Amsterdam)

June

Jun 01 Virtual Colloquium - Memorial Day Weekend
Esra Bulbul (Max Planck Institute for extraterrestrial Physics)
Jun 08 No Colloquium - Week of Summer AAS Meeting
Jun 15 Virtual Colloquium
Daniel Castro (Center for Astrophysics | Harvard & Smithsonian

A Glimpse into EHT-Scale Physics Using Movies and Polarization Maps

Richard Anantua

Center for Astrophysics | Harvard & Smithsonian, Flatiron Institute - Center for Computational Astrophysics, Event Horizon Telescope

Tuesday, Jan 26, 2021

Abstract

Recent radio observations of emission from infalling and outflowing plasma in the vicinity of supermassive black holes are linked to simple phenomenological models via general relativistic magnetohydrodynamic simulations using a methodology called "Observing" Jet (or outflow)/Accretion flow/Black hole (JAB) Simulations. For Sagittarius A* in our Galactic Center, movies simulating hourly timescales show that these models can be classified into at least four types: 1.) thin, asymmetric photon ring with best fit spectrum; 2.) coronal boundary layer with thin photon ring and steep spectrum; 3.) thick photon ring with flat spectrum; and 4.) extended outflow with flat spectrum. For M87, a self-similar, stationary, axisymmetric model based on a force-free flow in a HARM jet simulation is used to generate Stokes maps at Global mm-VLBI Array (86 GHz) and Event Horizon Telescope (230 GHz) scales. This model varies plasma content from ionic (e-p) to pair (e-e+). Emission at the observed frequency is assumed to be synchrotron radiation from electrons and positrons, whose pressure is set to relate to the local magnetic pressure through parametric prescriptions. Polarization maps are found to be sensitive to the positron effects of decreasing intrinsic circular polarization and increased Faraday conversion.

Experimental Neutrino Astrophysics and the Need for a Future Gamma-ray Observatory

Naoko Kurahashi Neilson

Drexel University

Tuesday, Feb 09, 2021

Abstract

IceCube is a high-energy neutrino observatory that aims to resolve sources of astrophysical neutrinos. Most of the source search analyses in IceCube rely extensively on gamma-ray observations, and particularly on Fermi observations because of the full-sky nature of the instrument. Despite our numerous searches correlating the GeV gamma ray band and the TeV neutirno band, no discoveries have been made to date, except for one strong evidence of a possible correlation. This talk will cover what the experimental neutrino astrophysics community wishes for in a gamma-ray instrument, and why it is crucial to have MeV observations, like AMEGO-X, for the future of neutrino astrophysics.

Quasars and Supermassive Black Holes: Uncovering Mysteries with Variability and Reverberation Mapping

Kate Grier

University of Arizonay

Tuesday, Feb 23, 2021

Abstract

Supermassive black holes, with masses that range from tens of thousands to billions of times the mass of our Sun, are thought to be present in nearly every galaxy in the Universe and may affect the growth and evolution of these galaxies. To understand how supermassive black holes interact with their host galaxies, we require accurate measurements of supermassive black hole masses in galaxies across the entire universe, as well as an understanding of their physical environments. We obtain this information by observing objects called active galactic nuclei, or quasars, which have supermassive black holes with large amounts of matter falling into them. These sources are highly variable, and we can use their variability to both measure their masses and learn about the physical environment very close to the black holes. We do this by examining the time delays between continuum flux variations and the response of distant gas as it reprocesses the ionizing radiation into emission lines which thus seem to “reverberate,” echoing the continuum variations; this technique is called reverberation mapping. In my talk, I will discuss supermassive black holes, active galactic nuclei/quasars, and the use of time variability -- primarily the technique of reverberation mapping -- to learn about these phenomena. I will focus specifically on my recent and planned work on large-scale reverberation-mapping projects using data from large surveys such as the Sloan Digital Sky Survey, which have allowed us to investigate large numbers of quasars at much greater distances than ever before.


Past Colloqia Schedules

2020: Fall, Spring
2019: Fall, Spring
2018: Fall, Spring
2017: Fall, Spring
2016: Fall, Spring
2015: Fall, Spring
2014: Fall, Spring
2013: Fall, Spring, Summer
2012: Fall, Spring
2011: Fall, Spring
2010: Fall, Spring

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