Research Events
For the Public
Northwestern University

Weekly Astrophysics Seminars 2014-2015

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 2015

  Date      Speaker / Seminar Host
  Jan. 20

Mariska Kriek
   UC Berkeley
    Reconstructing the Formation Histories of Massive Galaxies

In past years, large and deep photometric and spectroscopic surveys have significantly advanced our understanding of galaxy growth, from the most active time in the universe (z~2) to the present day. In particular, the evolution in stellar mass, star formation rate, and structure of complete galaxy samples have provided independent and complementary insights into their formation histories. In addition, detailed studies of the properties of distant galaxies have lead to a better apprehension of the physical processes which govern galaxy growth. Nonetheless, many outstanding questions remain. In this talk I will give an overview of our current picture of galaxy growth in the past 11 billion years, discuss current challenges and outstanding questions, and introduce new and ongoing efforts to further unravel the formation histories of massive galaxies.


  Jan. 27

Tom Abel
   Stanford University
    Dark Matter Dynamics

Computational Physics allows us to study extremely non-linear systems with fidelity. In astrophysical hydrodynamics and studies of galaxy formation much of the last two decades we have explored various discretization techniques and found subtle differences in some applications. Interestingly numerical studies of collisionless fluids such as e.g. the collapse of cold dark matter to form the large scale structure of the Universe has only been studied meaningfully with one approach; N-body Monte Carlo techniques. I will introduce a novel simulation approach, and demonstrate its feasibility, that for the first time can study a collisionless system in the continuum limit in multi-dimensions. I will also show this new technique opens a new window in making sense of structure formation as well as plasma physics. In this context we have developed a novel rasterization/voxelization algorithm applicable in computational geometry, computational physics, CAD design and other fields. I show how these approaches allow also for much improved predictions for gravitational lensing, dark matter annihilation, properties of cosmic velocity fields , and many other applications.

Fred Rasio

  Feb. 3

Joshua Peek
   Columbia University

Giles Novak

  Feb. 17

Lucianne Walkowicz
   Adler Planetarium and LSST

Aaron Geller

  Feb. 24

Sarah Gallagher
   University of Western Ontario
    Winds, Winds Every Where: Radiatively Driven Outflows from Supermassive Black Holes?

Supermassive black holes reside in the centers of every massive galaxy. In relatively brief spurts, black holes grow as luminous quasars through the infall of material through an accretion disk. Remarkably, the light from the accretion disk can outshine all of the stars in the host galaxy by a factor of a thousand, and this radiation can also drive energetic mass outflows. Mass ejection in the form of winds or jets appears to be as fundamental to quasar activity as accretion, and can be directly observed in many objects with broadened and blue-shifted UV emission and absorption features. A convincing argument for radiation pressure driving this ionized outflow can be made within the dust sublimation radius. Beyond, radiation pressure is still important, but high energy photons from the central engine can now push on dust grains. This physics underlies the dusty wind picture for the putative obscuring torus. I'll describe our model of the dusty wind and evaluate its success in accounting for observed properties of quasars such their mid-infrared spectral energy distributions, fractions of hidden objects, and column densities of important ions.

John Everett

  March 3

Mark Reid
   Harvard CfA

Farhad Zadeh


Spring Quarter 2015

  Date      Speaker / Seminar Host
  April 7

Dawn Erb
   University of Wisconsin, Milwaukee


  April 21

Geoffrey Vasil
   The University of Sydney


  May 19

Edwin Bergin
   University of Michigan
    Dissecting the Explosions and Environments of Nearby Supernovae

Evidence has mounted that Type Ia and core-collapse (CC) supernovae (SNe) can have substantial deviations from spherical symmetry; one such piece of evidence is the complex morphologies of supernova remnants (SNRs). In this talk, I will highlight techniques we have developed to ascertain the role of explosion geometry and environment in shaping these SNRs. I will discuss application of these methods to extensive multiwavelength data of Milky Way and Magellanic Cloud SNRs, and I will explore the implications regarding the nature of the progenitors and the dynamical evolution of these sources.

Farhad Zadeh

For more information, contact: Janet Howe (janet.howe@northwestern.edu)

Past Astrophysics Seminars