2010/03/31 by Brian D. Fields, Tijana Prodanović, Vasiliki Pavlidou +1 · 2 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Background radiation #COSMIC cancer database #Cosmic infrared background #Cosmology #Dark Matter and Cosmic Phenomena #Dark matter #Extragalactic background light #Fermi Gamma-ray Space Telescope #Galaxy #Gamma-ray bursts and supernovae #Observational cosmology #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1088/2041-8205/722/2/l199
published as The Astrophysical Journal Letters 722 (2010) L199 · 5 pages, 1 figure. Matches version published in ApJL. Sharper focus on normal (vs starburst) galaxies. Basic conclusions unchanged
openalex publication_date 2010/10/01 · arxiv created 2010/11/14 · arxiv updated 2010/11/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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 gamma rays; 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.