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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2132
DTSTART:20110303T213000Z
DURATION:PT1H0M0S
DTSTAMP:20240328T214927Z
LAST-MODIFIED:20110228T153359Z
LOCATION:4421 Sterling Hall
SUMMARY:The missing baryons around galaxies and galaxy clusters\, Astr
onomy Colloquium\, Joel Bregman\, University of Michigan
DESCRIPTION:The baryon content is composed of the sum of stars and the
gaseous
\ncomponents\, which can be measured in potential we
lls from the richest clusters to the poorest galaxies. For the riches
t clusters of galaxies\, most of the baryons are accounted for in that
the baryon fraction approaches the cosmological value\, within theore
tical expectations. Progressing toward shallower potential wells\, th
e baryon fraction decreases slowly until temperatures of about 1E6 K\,
below which the baryon fraction decreases quickly. This trend of dec
reasing baryon content continues through galaxies\, where the Milky Wa
y is missing about 75% of its baryons and the typical (lower mass) gal
axy is missing 90% of
\nits baryons. The missing baryons do
not surround the galaxies as hot halos and we argue that the material
never fell into these galaxies\, having been pre-heated by an early po
pulation of supernovae. Furthermore\, we show that the heating and me
tallicity contributions from this early population of stars may be lar
gely independent of galaxies as well.
URL:https://www.physics.wisc.edu/events/?id=2132
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