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The 2009 Fermi Symposium

Gamma Ray Probes of the Star Forming Universe and Cosmic-Ray History

Brian Fields, University of Illinois

Abstract:

Star formation produces supernovae and thus cosmic rays, whose propagation in the interstellar medium creates gamma rays. Fermi can resolve this emission in the Milky Way and in a few bright, nearby external galaxies, but the bulk of cosmic star formation produces an unresolved gamma-ray flux which possibly dominates the Fermi diffuse extragalactic background. We present a new calculation of the the expected hadronic signal from star-forming galaxies, and identify its observational signatures. Fermi detection of this signal (or strong limits on it!) will offer new probes of cosmic-ray origins, cosmic star formation, and the primordial lithium problem.