2016/05/31 by Hannes-S. Zechlin, H.-S. Zechlin, Alessandro Cuoco +5 · 45 citations
Health Professions · Mathematics · Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Gamma distribution #Gamma ray #Mathematics #Nuclear physics #Physics #Radiation Detection and Scintillator Technologies #Radioactivity and Radon Measurements #Statistics #astro-ph.HE
paper · pdf · doi:10.3847/2041-8205/826/2/l31
published in The Astrophysical Journal Letters 826(2), L31 (IOP Publishing) · 6 pages, 2 figures, 2 tables; v2: minor changes, accepted for publication in ApJL
arxiv created 2016/07/21 · openalex publication_date 2016/07/29 · arxiv updated 2016/08/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
ABSTRACT Statistical properties of photon count maps have recently been proven as a new tool to study the composition of the gamma-ray sky with high precision. We employ the 1-point probability distribution function of six years of Fermi -LAT data to measure the source-count distribution dN / dS and the diffuse components of the high-latitude gamma-ray sky as a function of energy. To that aim, we analyze the gamma-ray emission in five adjacent energy bands between 1 and 171 GeV. It is demonstrated that the source-count distribution as a function of flux is compatible with a broken power law up to energies of ∼50 GeV. The index below the break is between 1.95 and 2.0. For higher energies, a simple power-law fits the data, with an index of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> in the energy band between 50 and 171 GeV. Upper limits on further possible breaks as well as the angular power of unresolved sources are derived. We find that point-source populations probed by this method can explain <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>83</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> % ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>81</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>19</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>52</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> %) of the extragalactic gamma-ray background between 1.04 and 1.99 GeV (50 and 171 GeV). The method has excellent capabilities for constraining the gamma-ray luminosity function and the spectra of unresolved blazars.