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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


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.