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Astrophysics Seminars


The CASS Astrophysics Seminar features world-class astrophysicists from around the world speaking on current topics of research. Presentations are aimed at the graduate and post-graduate level, but are open to the general public. CASS seminars take place on Wednesdays from 4:00 - 5:00 p.m. in 383 SERF (Marlar Seminar Room), unless otherwise noted. You can watch a live stream of the talk or prior talks at the CASS Seminar YouTube Channel. The organizers are Prof. Shelley Wright and Prof. George Fuller.

Upcoming Seminars

Fall 2017

November 29, 2017

 "Cosmology Results from the Dark Energy Survey Year 1"

Elisabeth Krause
Research Scientist

 This talk presents cosmology constraints from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg2 of griz imaging data from the first year of the Dark Energy Survey (DES Y1). The analysis combines (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. These three measurements yield consistent cosmological results, and provide constraints on the amplitude of density fluctuations (S8 = 0.794+0.029-0.027) and dark energy equation of state (w = -0.80+0.20-0.22) that are competitive with those from Planck cosmic microwave background measurements.

I will describe the validation of measurements and modeling from catalogs to cosmology, and highlight cosmology constraints from the combination of DES Y1 with external data sets.

Based on DES Collaboration 2017 (1708.01530) and supporting papers.

December 6, 2017

 "The Breakthrough Listen Search for Advanced Life Beyond Earth”

Andrew Siemion
Director, Berkeley SETI Research Center
UC Berkeley

 The Breakthrough Listen Initiative is an ambitious effort to conduct the most comprehensive and sensitive search for advanced extraterrestrial life in humanity’s history. Breakthrough Listen has secured approximately 20% of the time on two of the largest radio telescopes in the world, the 64m Parkes Telescope in NSW, Australia and the 100m Green Bank Telescope at Green Bank Observatory in West Virginia, along with 36 nights per year on the 2.4m Automated Planet Finder at Lick Observatory. Breakthrough Listen has also entered into an agreement with the National Astronomical Observatory of China to collaborate on the development of search techniques, software and observing procedures for the 500m FAST Telescope, and the Jodrell Bank Observatory / University of Manchester to work together in a similar fashion toward developing SETI capabilities on the 76m Lovell Telescope and the MERLIN network.

Breakthrough Listen observations at the APF employ the Levy Spectrometer to conduct ``spectroscopic optical SETI’’ observations, searching for artificially narrow spectral lines that are known only to arise from technological sources (lasers). At the GBT and Parkes, Breakthrough Listen is deploying state-of-the-art digital backends capable of searching for a wide variety of signals indicative of a technological source, across many GHz of instantaneous bandwidth. As of this writing, Breakthrough Listen has deployed a 6 GHz system at the Green Bank Telescope and a 5 GHz system at the Parkes Telescope.

The current Breakthrough Listen target list includes a spectral-type complete sample of nearby stars, 100 nearby galaxies spread over all morphological types, a complete survey of the galactic plane and exotic objects and targets of opportunity (e.g. KIC 8462852, FRB121102). The Breakthrough Listen team is currently exploring opportunities to engage in commensal SETI programs with the SKA and its precursors. These potential extensions to the Breakthrough Listen program would allow significant expansion of the Breakthrough Listen target list and would lay the groundwork for extremely high sensitivity observations with the full SKA. These latter observations would be the first SETI ever conducted that would be sensitive to Earth-level leakage radiation from nearby stars.

Here I will review the Breakthrough Listen program, current observational capabilities and latest results.

Winter 2018

January 10, 2018

Brandon Hensley
Postdoctoral Fellow

January 17, 2018

 "Analysis of dust emission in nearby galaxies - Implications of the modeling

Jérémy Chastenet
Postdoctoral Scholar

 My work focused on the implications of dust emission modelisation choices on its derived properties in nearby galaxies. A first approach showed that all models do not fit observations of two nearby galaxies adequately and similarly, although they all managed to fit the Milky Way infrared emission. It also highlighted that the dust composition is not the same between those two galaxies, and also with that of the Milky Way. The choice of the dust grains environment, through the incident radiation field, can significantly impact results like the total dust masses. A second project investigated the systematics errors due to the empirical laws used to describe theradiation field that heats the dust grains. I showed that some parameters can be over- or underestimated, while showing good fits to the observations. By getting rid of uncertainties due to dust composition, my results show that the current approach leads to discrepancies in the dust content in spite of a correct dust description.

January 24, 2018

Victor Robles
Postdoctoral Researcher
UC Irvine

January 31, 2018

 "Breaking the Habit - The peculiar 2016 eruption of the remarkable recurrent nova
in M31"

Martin Henze
San Diego State University

 Since its discovery in 2008, the Andromeda galaxy nova M31N 2008-12a has been observed in eruption every single year. This unprecedented frequency indicates an extreme object, with a massive white dwarf and a high accretion rate, which is the most promising candidate for the progenitor of a type-Ia supernova known to date. The previous three eruptions of M31N 2008-12a have displayed remarkably homogeneous multi-wavelength properties. In contrast, the delayed 2016 eruption (in December last year) showed significant deviations from this pattern. In this talk, I will discuss the 2016 observing campaign and its results, together with possible interpretations on the physics and evolution of this unique system in the context of extragalactic nova science.

February 7, 2018

NOTE: Joint Astro-Plasma Physics Seminar

Ellen Zweibel
W. L. Kraushaar Professor of Astronomy & Physics, Department of Astronomy
University of Wisconsin-Madison

February 14, 2018

Joy Didier
UC Santa Cruz

February 28, 2018

John Tomsick
Researcher, Space Sciences Lab
UC Berkeley

March 7, 2018

Emily Pringle
Scripps Postdoctoral Fellow

Spring 2018

April 25, 2018

Jorge Pineda
Research Scientist

May 9, 2018

Jessica Werk
Assistant Professor
University of Washington

May 30, 2018

Ruth Murray-Clay
UC Santa Cruz