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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-1600
DTSTART:20091006T203000Z
DURATION:PT1H0M0S
DTSTAMP:20260422T030812Z
LAST-MODIFIED:20090901T134938Z
LOCATION:3425 Sterling Hall
SUMMARY:Planetary Nebulae and the Structure and Kinematics of Galactic
  Disks\, Astronomy Colloquium\, Robin Ciradullo\, Penn State
DESCRIPTION:Much of our understanding of dark matter halos comes from 
 the largely-untested assumption that the mass-to-light ratio of spiral
  disks is constant is radius.  To test this hypothesis\, we have used 
 planetary nebula kinematics to measure the disk mass surface density o
 f five nearby\, low-inclination spiral galaxies.  We show that\, in ge
 neral\, disks do have a constant M/L out to ~ 3 optical scale lengths\
 , but once outside this radius\, the vertical velocity dispersion of o
 ld disk stars is independent of distance.  We suggest that this is due
  to the increased importance of a thick disk\, and possible disk heati
 ng of the thin disk by dark halo substructure.  We show that the disks
  of early type spirals have higher M/L values and are closer to maxima
 l than the disks of later-type spirals\, and that the residual unseen 
 dark halos are better fit by pseudo-isothermal laws than by NFW profil
 es.
URL:https://www.physics.wisc.edu/events/?id=1600
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