Source Count Distribution of Fermi LAT Gamma-Ray Blazars Using Novel Nonparametric Methods

Abstract

We utilized a sample from the Fermi-LAT 14-year Source Catalog by adjusting the flux detection threshold, enabling us to derive the intrinsic source count distribution $dN/d{F}_{25}$ of extragalactic blazars using nonparametric, unbinned methods developed by Efron and Petrosian and Lynden-Bell. Subsequently, we evaluated the contribution of blazars to the extragalactic gamma-ray background. Our findings are summarized as follows: (1) There is no significant correlation between flux and spectral index values among blazars and their subclasses FSRQs and BL Lacs. (2) The intrinsic differential distributions of flux values exhibit a broken-power-law form, with parameters that closely match previous findings. The intrinsic photon index distributions are well described by a Gaussian form for FSRQs and BL Lacs individually, while a dual-Gaussian model provides a more appropriate fit for blazars as a whole. (3) Blazars contribute 34.5\% to the extragalactic gamma-ray background and 16.8\% to the extragalactic diffuse gamma-ray background. When examined separately, FSRQs and BL Lacs contribute 19.6\% and 13\% to the extragalactic gamma-ray background, respectively.

14 pages, 6 figures. Accepted for publication in Universe

References in corpus (10)

• The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV
• Gamma-Ray Studies of Blazars: Synchro-Compton Analysis of Flat Spectrum Radio Quasars
• The Fermi-LAT high-latitude Survey: Source Count Distributions and the Origin of the Extragalactic Diffuse Background
• The Spectral Energy Distributions of Fermi Blazars
• The Konus-Wind catalog of gamma-ray bursts with known redshifts. I. Bursts detected in the triggered mode
• Cosmological Evolution of Long Gamma-ray Bursts and Star Formation Rate
• An unexpectedly low-redshift excess of Swift gamma-ray burst rate
• Discerning the $\gamma$-ray emitting region in the flat spectrum radio quasars
• Gamma-ray Luminosity and Photon Index Evolution of FSRQ Blazars and Contribution to the Gamma-ray Background
• Source-count Distribution of Gamma-Ray Blazars