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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-1999
DTSTART:20101111T213000Z
DTEND:20101111T230000Z
DTSTAMP:20260416T005506Z
LAST-MODIFIED:20101011T161516Z
LOCATION:4421 Sterling Hall
SUMMARY:Photoionization of High Altitude Gas in a Supernova-Driven Tur
 bulent Interstellar Medium\, Astronomy Colloquium\, Kenny Wood\, Unive
 rsity of St Andrews\, School of Physics and Astronomy
DESCRIPTION:One of the major questions in studies of widespread diffus
 e ionized gas in galaxies is how ionizing photons can penetrate from O
 B stars in midplane regions to ionize gas at large heights above the p
 lane. A three dimensional ISM provides the solution - low density void
 s allow photons to travel much farther than in a smoothly distributed 
 ISM. I will show new results of photoionization calculations in a 3D S
 upernovae driven hydro simulation of the ISM. Ionizing photons can eas
 ily reach to large distances from the midplane. However\, the resultin
 g emission measure distributions are broader than observed in the Milk
 y Way and other galaxies. A possible reason for this is the absence of
  magnetic fields in the dynamical simulations. Our simulations also pl
 ace limits on the survivability of neutral clouds in the Galactic halo
  exposed to the ionizing radiation percolating through the models. I w
 ill also summarize recent Spitzer observations of gas many kiloparsecs
  from the midplane of the edge-on galaxy NGC891 that indicate an addit
 ional population of very hot ionizing sources are required to explain 
 the observed emission line ratios.
URL:https://www.physics.wisc.edu/events/?id=1999
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