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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-4937
DTSTART:20181101T203000Z
DTEND:20181101T220000Z
DTSTAMP:20260407T175639Z
LAST-MODIFIED:20181022T154606Z
LOCATION:4421 Sterling Hall\, Coffee and Cookies 3:30 PM\, Talk begins
  at 3:45 PM
SUMMARY:Survey of the Large-Scale Flows of Baryons Around Galaxies\, A
 stronomy Colloquium\, Nicholas Lehner\, University of Notre Dame
DESCRIPTION:It has become clear that the level of activity in a galaxy
  is affected by phenomena occurring in its disk\, but also in its halo
 \, known as the circumgalactic medium (CGM) --  the gas at the interfa
 ce of a galaxy and the intergalactic medium. Gas flows through the CGM
  directly influence the baryon distribution and metal content of their
  host galaxies as well as the level of stellar activity in the disk\, 
 and hence the evolution of galaxies. The metallicity is a key paramete
 r that allows us to directly determine the level and type of enrichmen
 t of the CGM gas and its possible origin(s). I will present an HI-sele
 cted absorption-line survey of the gas at low and high redshift where 
 we estimated the metallicity of the gas for several hundreds of CGM ab
 sorbers. I will show that there is a a significant fraction of the CGM
  that is metal rich at any z. I will show that there is surprisingly a
 lso a large reservoir of metal-poor gas at any z\, some of this gas sh
 owing little chemical enrichment over several billions of years. I wil
 l argue that this metal-poor gas might be the long-sought cold flow ac
 cretion that provides a source of gas for ongoing star-formation over 
 billions of years in cosmological simulations. I will finally discuss 
 these observational results in the context of recent cosmological simu
 lations and future radio 21-cm HI emission surveys.  <br>
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URL:https://www.physics.wisc.edu/events/?id=4937
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