Cosmic gamma-ray background from star-forming galaxies

Brian D. Fields, Vasiliki Pavlidou, Tijana Prodanović

Research output: Contribution to journalArticlepeer-review


The origin of the extragalactic gamma-ray background is a pressing cosmological mystery. The Fermi Gamma- Ray Space Telescope has recently measured the intensity and spectrum of this background; both are substantially different from previous measurements. We present a novel calculation of the gamma-ray background from normal star-forming galaxies. Contrary to long-standing expectations, we find that numerous but individually faint normal galaxies may comprise the bulk of the Fermi signal, rather than rare but intrinsically bright active galaxies. This result has wide-ranging implications, including: the possibility to probe the cosmic star formation history with gammarays; the ability to infer the cosmological evolution of cosmic rays and galactic magnetic fields; and an increased likelihood of identifying subdominant components from rare sources (e.g., dark matter clumps) through their large anisotropy.

Original languageEnglish (US)
Pages (from-to)L199-L203
JournalAstrophysical Journal Letters
Issue number2 PART 2
StatePublished - Oct 20 2010


  • Cosmic rays
  • Galaxies: star formation
  • Gamma rays: diffuse background
  • Gamma rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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