Resolving the Small-Scale Structure of the Cool Circumgalactic Medium

Prof. Kate Rubin (San Diego State University)
September 27, 2017 - 4:00pm


The environments extending several hundred kiloparsecs from galaxies contain the fuel that feeds galactic star formation, and act as the reservoir into which ejecta from stellar and AGN feedback are driven.  Observations of the cool hydrogen and metal content, kinematics, and morphology in these regions (i.e., the circumgalactic medium, or CGM) therefore test our understanding of these processes.  Background quasar spectroscopy has long been the tool of choice for such observations; however, spectroscopy of bright galaxies can also be used to study the halos of galaxies in the foreground.  I will describe a Keck/LRIS and VLT/FORS2 survey which uses this technique to characterize cool gas in individual foreground galaxy halos, and which yields a unique constraint on the coherence scale of MgII absorption in the z~0.5 CGM.  I will discuss the implications of this constraint for the lifetime and fate of the cool absorbing structures.  I will then describe new measurements of gas flows made possible with the spatially-resolved galaxy spectroscopy being obtained by the SDSS-IV/MaNGA survey, demonstrating MaNGA's potential for establishing the frequency and cross section of gas accretion onto galaxies.  Such three-dimensional study is crucial to understanding the thermodynamics of the gas flows which regulate galaxy growth.