Diffuse Gamma-rays from Star Forming Galaxies

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Diffuse Gamma-rays from Star Forming Galaxies

• Tim Paglione
• York College, CUNY
• Boston GLAST Workshop, June 21, 2007

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Gamma-rays from Normal Galaxies
pion bump

• A.k.a. foreground contamination
• Interactions between cosmic rays and interstellar
  matter radiation
• Inverse Compton scattering
• Bremsstrahlung
• Neutral pion decay

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Gamma-rays from Starbursts

• Inverse Compton scattering
• Enhanced (IR) photon density from numerous
  clusters of young massive stars
• Bremsstrahlung
• Enhanced cosmic ray density from numerous
  supernova explosions
• Neutral pion decay
• Enhanced proton density in massive molecular
  clouds

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Gamma-rays from Starbursts

• Only upper limits from EGRET
• Paglione et al. 1996 Blom, Paglione
  Carramiñana 1999 Cillis, Torres Reimer 2005)

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Promise of GLAST

• Better sensitivity better resolution
• Follows extensive surveys in IR, radio and
  molecular gas emission
• Improved models of pion production
• Extends to very high energies (CANGAROO?)
• Probe X N(H2)/ICO in other galaxies, cosmic ray
  diffusion (radio/IR correlation), etc.