Source-count Distribution of Gamma-Ray Blazars

Abstract

With ten years of operation and an exceptional dataset, the Fermi-Large Area Telescope allows us to unveil the detailed composition of the extragalactic $\gamma$-ray sky above $100\mathrm{MeV}$. In this paper, we derive the intrinsic source-count distribution (logN-logS) of extragalactic sources (i.e., blazars) at $|b|>20^{\circ }$ via the efficiency correction method. With this approach, we are able to measure the distribution down to a photon flux of $\sim 10^{-10}$$\mathrm{ph}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ and to an energy flux of $\sim 10^{-12}$$\mathrm{erg}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$. In both cases the logN-logS becomes flatter at low fluxes. Moreover, we show that this logN-logS is representative of the blazar population (assuming the majority of unassociated sources are blazars) and allows us to constrain its evolution quite effectively. Among recently proposed evolutionary models, we find that the Pure Density Evolution (PDE) model best describes the evolutionary properties of the blazar population and that their integrated emission accounts for $\sim 50_{-5}^{+10}\%$ of the total extragalactic \gm-ray background.

16 pages, 9 figures, 5 tables; published in the Astrophysical Journal

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Cited by in corpus (1)

• Gamma-ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei