astro seminar

Astro Seminar

Date: 
Wednesday, October 12, 2022 - 3:00pm
Location: 
CP179 and on zoom
Type of Event (for grouping events):

THE GALEX EXTRAGALACTIC SPECTRA DATA BASE

Abstract: 
 
We have matched objects in the Galaxy Evolution Explorer (GALEX) spectroscopic fields with publicly available ultraviolet, optical, and infrared surveys, to construct a photometric and spectroscopic catalog for non-stellar objects with GALEX spectroscopic counterparts. Of the total sample of GALEX spectra recorded in the database, approximately 20\% are determined to reliably correspond to non-stellar objects. These objects have been cross-matched with SDSS, WISE, and 2MASS photometric and spectroscopic survey catalogs, and VISTA and UKIRT near-IR catalogs where available, to construct spectral energy distributions (SED's) from the GALEX-FUV to WISE-w4 magnitudes for all non-stellar objects within the fields. Analysis of 209 fields with at least one object matched in SDSS give a total of 12,020 extragalactic objects, comprising 1974 known QSOs and AGNs, 2274 star-forming galaxies, 6327 quiescent spiral galaxies, and 386 elliptical galaxies.

 

Astro Seminar

Date: 
Wednesday, November 9, 2022 - 3:00pm
Location: 
CP179 and on zoom
Type of Event (for grouping events):
TBA

Astro Seminar

Date: 
Wednesday, November 9, 2022 - 3:00pm
Location: 
CP179 and on zoom
Type of Event (for grouping events):
TBA

Astro Seminar

Date: 
Wednesday, December 7, 2022 - 3:00pm
Location: 
CP179 and on zoom
Type of Event (for grouping events):
TBA

Astro Seminar

Date: 
Wednesday, November 16, 2022 - 3:00pm
Type of Event (for grouping events):
TBA

Astro Seminar

Date: 
Wednesday, October 26, 2022 - 3:00pm
Location: 
CP179 and on-zoom
Type of Event (for grouping events):
TBA

Astro seminar

Date: 
Wednesday, October 19, 2022 - 3:00pm
Location: 
CP179 and on zoom
Type of Event (for grouping events):
TBA

Astro Seminar

Date: 
Wednesday, September 28, 2022 - 3:00pm
Location: 
CP179 and on-zoom
Tags/Keywords:
Type of Event (for grouping events):

Black hole accretion flows: from nearby stellar binaries to quasars at cosmic dawn

Accretion onto black holes transforms the darkest objects in the universe into the brightest. I will review what we know about the emission from the accretion flow, starting with the stellar mass black holes in binary systems in our own galaxy. Scaling up to the supermassive black holes in active galaxies and quasars reveals both similarities and differences. One of the key similarities is the 'changing look' phenomena in active galaxies, where the UV continuum associated with an optically thick accretion flow drops over a few months/years, triggering the disappearance of the characteristic broad emission lines, analogous to the state transition in binaries. One of the key differences is the nature of the accretion flow above the transition luminosity, where the stellar mass black holes look like standard discs and have variability timescales like standard discs while the supermassive ones do not. Only at the highest luminosities (extreme narrow line Seyfert 1 galaxies and the weak line quasars) does the accretion flow match to the disc models. I will speculate on the physics underlying all the behavior, and give a united picture of the accretion flow.

 

 

 

Introduction to the SDSS-V Milky Way Mapper

Date: 
Wednesday, November 10, 2021 - 3:00pm
Location: 
Blazer Dining 339 (on zoom)
Tags/Keywords:
Type of Event (for grouping events):
The fifth incarnation of the Sloan Digital Sky Survey (SDSS-V) began taking data last year and is in the process of transitioning to the use of a robotic positioning system. I will described the SDSS-V Milky Way Mapper program and its goals. The first of its major goals is to understand the history and structure of the Milky Way. Following upon work done with the APOGEE-1 and 2 surveys the Milky Way Mapper will use approximately 6 million stars to trace out the detailed structure of the Galaxy. The second major goal is to understand stellar astrophysics. The Milky Way Mapper contains several smaller programs called cartons, whose goals cover a wide variety of stellar candidates including white dwarfs, binary stars, young stellar objects, planet hosts, asteroseismology targets and x-ray binaries. These cartons will allow us to explore all sorts of interesting topics that can only be done with a large-scale spectroscopic survey. I will give updates on the current progress of the survey, and lay out our plans for the future.

Multi-messenger Observations of the Most Relativistic Cosmic Bangs: from Outflows to Remnants

Date: 
Wednesday, October 27, 2021 - 3:00pm
Location: 
Blazer Dining 339 (on zoom)
Tags/Keywords:
Type of Event (for grouping events):
The deaths of massive stars seed our universe with black holes and neutron stars - the most exotic objects of the stellar graveyard. The births of these stellar remnants, as well as their mergers when paired in binaries, power explosions that can launch the most relativistic jets we know of in the universe (gamma-ray bursts) and shake the very fabric of space-time via ripples called gravitational waves. GW170817, the merger of two neutron stars witnessed through both its gravitational wave siren and its glow at all wavelengths of light, represents the first multi-messenger detection of one such extreme cosmic bang. Starting from the example of GW170817, in this talk I will discuss how radio light in particular, and gravitational waves, can be used in tandem to unveil the physics of relativistic transients. I will also highlight opportunities and challenges that lie in front of us, as improvements in detectors’ sensitivities will transform a trickle of multi-messenger discoveries into a flood.

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