γ-RAY LUMINOSITY FUNCTION AND THE CONTRIBUTION TO EXTRAGALACTIC γ-RAY BACKGROUND FORFERMI-DETECTED BLAZARS

Abstract

We study γ-ray luminosity functions (GLFs) and the contribution to the extragalactic diffuse γ-rays for blazars. After using a clean blazar sample in which 485 blazars are observed at both the 8.4 GHz and ∼ GeV bands, we investigate the radio/γ-ray luminosity correlation and find out that a strong correlation exists between the radio and γ-ray luminosities using the partial correlation analysis method. Based on such a correlation, we obtain the GLF, while also considering the GLF based on studies of the X-ray luminosity function of active galactic nuclei and the GLF of the EGRET blazars. K-S tests indicate that these three kinds of GLFs are consistent with the observed data of our sample in a reasonable parameter range. Using these GLFs, we further investigate the blazar contribution to the extragalactic diffuse γ-ray background (EGRB). Our results show that (1) the contribution of blazars are ∼21.3% ±2.7%, ∼12.9% ±1.7%, and ∼37.9% ±4.8% of unresolved Fermi EGRB flux for the three GLFs and (2) the contribution of flat-spectrum radio quasars are ∼11.2% ±1.6%, ∼6.9% ±1.0%, and ∼9.0% ±1.2% of unresolved Fermi EGRB flux for the three GLFs.