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Northwestern University


Weekly Astrophysics Seminars 2015-2016

Seminars are held at 4:00 PM on Tuesdays in Room F160
on the first floor of the Technological Institute (2145 Sheridan Road) unless otherwise noted

 

Winter Quarter 2016

  Date      Speaker / Seminar Host
  Feb. 16

Ben Bar-Or
   Institute for Advanced Study
   Stellar Dynamics around a Massive Black Hole

Galactic nuclei and the Massive black holes (MBHs) in their centers are rich environments, where the complex stellar dynamics plays an important role in many physical phenomena. We show that the standard description of the two-body relaxation, around an MBH, as a diffusion process, is incomplete. We derived a non-perturbative solution for energy relaxation as an anomalous diffusion process, and a robust estimation technique to measure it in N-body simulations. We also show how the dynamics of a nearly-Keplerian N-body system, where the angular momentum evolution is accelerated by resonant relaxation, can be described and studied in a formal statistical mechanics framework. In this framework the background potential is described as a correlated Gaussian noise. We obtained the leading order, phase-averaged stochastic equations of motion and derived an effective Fokker-Plank equation for a general correlated Gaussian noise. We combine the Fokker-Plank description of two-body relaxation and resonant relaxation to study the loss-cone dynamics in Galactic nuclei.

Fabio Antonini

  Feb. 23

Leslie Looney
   University of Illinois at Urbana-Champaign
   Setting the Initial Conditions for Planets: The Young Circumstellar Disk

The origin and evolution of the circumstellar disk around protostars informs the origin and evolution of planets. Only recently, have we even detected the youngest circumstellar disks, but their frequency and typical properties (i.e. mass and size) are still not well known. With our new high-resolution millimeter surveys of protostars, we now have about 20 young disks with radii > 15 AU. However, these only represent less than of the population in our surveys. One possible explanation for small disks (< 15AU) in the youngest sources is magnetic braking of material at the earliest stages. In this talk, I explore the early evolution of the disk, implications for dust growth, and discuss future surveys.

Laura Fissel

  Mar. 1

Julie Hlavacek-Larrondo
   Université de Montréal
   AGN Feedback in Brightest Cluster Galaxies

The last few decades have shown us that radio jets originating from supermassive black holes can interact strongly with their surrounding medium. During this talk, I will review the current status of this field, known as AGN feedback, while focusing on the most massive black holes in the Universe, those that lie in Brightest Cluster Galaxies, the central dominant galaxies in galaxy clusters. I will review the physics behind these interactions and then focus on the evolution of radio feedback over cosmic time while presenting new results from clusters discovered via the South Pole Telescope.

Claude-André Faucher-Giguère

 

Spring Quarter 2016

  Date      Speaker / Seminar Host
  Mar. 29

Laura Chomiuk
    Michigan State University
    The E-Nova Project: A Multi-Wavelength Initiative to Probe the
    Ejecta and Environments of Novae

When imagining a nuclear explosion, we often picture strong, spherical shock waves, like a bomb or supernova; however, nature's most common thermonuclear explosions look nothing like this, showing delayed and multiple phases of mass ejection that can last for months after the nuclear fuel is ignited. These most common explosions are novae---thermonuclear runaways on the surfaces of accreting white dwarfs---and their complexities are best revealed with an intensive multi-wavelength observational program highlighting radio and X-ray data---our E-Nova Project. I will discuss our recent results, featuring observations from the Karl G. Jansky Very Large Array, and spotlighting sources like recent novae with giant companions and novae that have recently been detected in GeV gamma rays (an emission process that was not predicted and remains an intriguing mystery).

Fred Rasio,
Sourav Chatterjee

  Apr. 12

Alycia Weinberger
   Carnegie Institution of Washington

Fred Rasio

  Apr. 26

Ilse Cleeves
   Harvard-Smithsonian Center for Astrophysics

Sourav Chatterjee

  May 3

Matteo Cantiello
   Kavli Institute for Theoretical Physics

Sourav Chatterjee

  May 10

Xavier Siemens
   University of Wisconsin-Milwaukee

Vicky Kalogera

  May 17

Daniel Jontof-Hutter
   Pennsylvania State University

Sourav Chatterjee

  May 24

Wen-fai Fong
   University of Arizona

Vicky Kalogera,
Niharika Sravan,
and Fani Dosopoulou

  May 31

Jonathan Trump
   Pennsylvania State University

Daniel Angles-Alcazar


For more information, contact: ciera@northwestern.edu


Past Astrophysics Seminars