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SUMMARY:Thermodynamics of the Hot Gas in Galaxies\, Groups\, &amp\; Cluste
 rs - Ian McCarthy\, Kavli Institute for Cosmology\, University of Cambridg
 e
DTSTART:20081030T163000Z
DTEND:20081030T173000Z
UID:TALK13617@talks.cam.ac.uk
CONTACT:Dr. Vasily Belokurov
DESCRIPTION:Only ~10 per cent of baryons in the Universe are in the form o
 f stars\, yet most models of luminous structure formation have concentrate
 d on the properties of the stellar matter.  In this talk I will focus on t
 he "flip side" of galaxy formation and investigate the properties of the m
 aterial that is not presently locked up in galaxies. This "by-product" of 
 galaxy formation can be observed as an X-ray emitting plasma [the intraclu
 ster medium (ICM)] in groups and clusters. Since a significant fraction of
  this material has been processed through galaxies\, observations of the I
 CM represent an orthogonal set of constraints on galaxy formation models.\
 n\nI first review the state of the hot gas in massive galaxy clusters\, wh
 ere the observational X-ray data is of the highest quality.  Using a simpl
 e model\, I will argue that the energetics required to the establish the d
 istribution of the gas in these systems is beyond the reach of present-day
  AGN and that a significant degree of so-called "preheating" is required. 
  While preheating models successfully reproduce the present-day properties
  of the ICM\, they have profound implications for the evolution of the ICM
  and the state of the gas in galaxies and galaxy groups - namely \nthat th
 ere should be large numbers of very X-ray underluminous galaxies and group
 s.  I will discuss the observational evidence for such systems. \nIn the s
 econd part of the talk\, I will present preliminary results from \ntwo new
  sets of cosmological hydrodynamic simulations (the OverWhelmingly Large S
 imulations\, OWLS\, and the Galaxies-Intergalactic Medium Interaction Calc
 ulation\, GIMIC).  These simulations place the preheating scenario in a st
 ronger physical context and make falsifiable predictions for upcoming surv
 eys.\n\n\n
LOCATION:Sackler Lecture Theatre\, IoA (tea at 4.00 pm)
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