PoS - Proceedings of Science
Volume 301 - 35th International Cosmic Ray Conference (ICRC2017) - Session Gamma-Ray Astronomy. GA-extra-galactic
The gamma-ray source-count distribution as a function of energy
H. Zechlin
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Pre-published on: August 16, 2017
Published on: August 03, 2018
Photon counts statistics have been shown to provide a sensitive tool for characterizing gamma-ray source populations and the composition of the gamma-ray sky. In this contribution, we extend the use of the standard 1-point probability distribution function (1pPDF) to decompose the high-latitude gamma-ray flux observed with Fermi-LAT into emission from point sources, Galactic foreground, and diffuse isotropic background. To that aim, we perform an energy-binned analysis of the gamma-ray data between 1 and 171 GeV. We measure the source-count distribution $\mathrm{d}N/\mathrm{d}S$ in several energy bins, and we demonstrate that our results extend current measurements driven by point-source catalogs to so far undetected source contributions. The source-count distribution as a function of flux is found to be compatible with a broken power law. Upper limits on further possible breaks as well as the angular power of unresolved sources are derived. We discuss the composition of the gamma-ray sky and future prospects and capabilities of the 1pPDF method.
DOI: https://doi.org/10.22323/1.301.0644
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