Caltech Home > PMA Home > Calendar > TAPIR Seminar
open search form
Friday, November 05, 2021
2:00 PM - 3:00 PM
Cahill 370

TAPIR Seminar

What's Happening in Halos?
J. Michael Shull, Professor, Astrophysical and Planetary Sciences, University of Colorado at Boulder,

Hybrid -- To Join via Zoom

This seminar is a "prequel" to my IPAC Seminar (Nov 10) which is entitled "Where Do Galaxies End?".  Halos of galaxies can terminate either by gravity or by gas.  Constraints from absorption and emission studies (UV and X-ray) suggest radial extents of 150-250 kpc.  I will start with a discussion of physical processes that influence galactic-wind termination at the "galactopause" or allow breakout of the circumgalactic medium ( CGM) into the intergalactic medium (IGM).  In typical halo gas (T = 10^6 K and_H = 10^-4 cm^-3) radiative cooling times exceed 1 Gyr. Thus, thermal instabilities likely require compressional triggers to produce kiloparsec-scale clumps, which lose pressure support and fall inward at rates of several solar masses/year.  I will conclude by showing new 3D hydrodynamical models (with Fabian Heitsch) of Galactic high velocity clouds, including stripping, mixing with halo gas, and re-accretion of gas in the wake of the cloud ("Peloton Effect"). 

For more information, please contact JoAnn Boyd by phone at 626-395-4280 or by email at