The Growth and Enrichment of the Intragroup Gas
  The thermal and chemical properties of the hot diffuse intragroup medium
(IGrM) provide important constraints on the feedback processes associated with
massive galaxy formation and evolution. Here we explore these constraints via a
detailed analysis of the global properties of simulated z<3 galaxy groups from
a cosmological simulation that includes a well-constrained prescription for
stellar/supernovae-powered galactic outflows but no AGN feedback. Our aims are
to (a) establish a baseline against which we will compare future models; (b)
identify model successes due to stellar/supernovae-powered outflows; and (c)
pinpoint features that signal the need for, and constrain the nature of, AGN
feedback.
  Our simulation successfully reproduces key observed z=0 group IGrM
properties, including the various X-ray Lx - Tx - entropy scaling relations,
for all but the most massive groups. The z<1 redshift evolution of these also
agree with observations. Contrary to expectations, the simulated groups' IGrM
does not suffer catastrophic cooling. Yet, the z=0 group stellar mass is ~ 2X
too large. This is due to the build-up of cold gas in the massive galaxies
before they are incorporated inside groups. This in turn indicates that other
feedback mechanisms must activate in real galaxies once their stellar masses
grow to a few X 10^{10} M_sun. We show that these must be powerful enough to
expel a significant fraction of the gas from the galactic halos. Gentle
maintenance-mode (quenching) AGN feedback, as seen in galaxy clusters, will not
do. Just as importantly, we find that the stellar/supernovae-powered winds are
essential for understanding the IGrM metal abundances. Our simulation is able
to reproduce the observed relationship between the global IGrM iron and silicon
abundance and the group X-ray temperature, and these results ought to be
relatively insensitive to the addition of AGN feedback.
