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VERSION:2.0
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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-1044
DTSTART:20080226T214500Z
DURATION:PT1H0M0S
DTSTAMP:20260423T055121Z
LAST-MODIFIED:19700101T060000Z
LOCATION:6515 Sterling Hall (coffee at 3:30 pm in 6521 Sterling)
SUMMARY:The Stellar Populations of the Andromeda Spiral Galaxy\, Astro
 nomy Colloquium\, Jason Kalirai\, University of California - Santa Cru
 z
DESCRIPTION:Simulations of hierarchical galaxy formation suggest that 
 large galaxies such as the Milky Way and Andromeda (M31) should contai
 n extended stellar halos that are chemically distinct (more metal poor
 ) from the inner spheroid. Yet\, no such population has been discovere
 d in our nearest neighbor\, M31. We report on the first results from a
  photometric and spectroscopic survey of red giant branch (RGB) stars 
 over a large expanse in M31. Using a new technique based on photometri
 c and spectroscopic diagnostics\, we are able to isolate bonafide M31 
 RGB stars out to a distance five times further than previous studies (
 165 kpc). In addition to the kinematically cold disk and metal-rich in
 ner spheroid\, we find clear evidence for an extended\, power law halo
  component in M31. The spectroscopic and photometric metallicity of th
 is new population is measured independently and found to be metal-poor
 \, [Fe/H] = -1.5. We also present the discovery of a new dwarf spheroi
 dal galaxy in M31 and evidence for spatial and kinematical substructur
 e in the halo. The discovery of this stellar halo puts to rest much of
  the disparity that has existed between the Milky Way and M31 halos\, 
 and brings forth an ideal testbed for detailed simulations of galaxy f
 ormation.
URL:https://www.physics.wisc.edu/events/?id=1044
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