Cosmological Evolution of Fermi-LAT Gamma-ray Blazars Using Novel Nonparametric Methods

TL;DR

This paper applies novel non-parametric statistical methods to analyze the cosmological evolution of gamma-ray blazars' luminosity function, revealing intrinsic luminosity correlations and contributions to the gamma-ray background.

Contribution

It introduces a new non-parametric approach dividing samples into sub-samples with different flux limits for unbiased evolution analysis.

Findings

Determined the gamma-ray luminosity function and its evolution for blazars.

Estimated the intrinsic correlation between gamma-ray and optical luminosities.

Quantified blazars' contribution to the extragalactic gamma-ray background.

Abstract

Multi-wavelength analyses of spectra of active galactic nuclei (AGNs) provide useful information on the physical processes in the accretion disk and jets of black holes. This, however, is limited to bright sources and may not represent the population as a whole. Another approach is through the investigation of the cosmological evolution of the luminosity function (LF) that shows varied evolution (luminosity and density) at different wavelengths. These differences and the correlations between luminosities can shed light on the Jet-accretion disk connection. Most such studies use forward fitting parametric methods that involve several functions and many parameters. We use non-parametric, non-binning methods developed by Efron and Petrosian, and Lynden-Bell, for obtaining unbiased description of the evolution of the LF, from data truncated by observational selection effects. We present analysis of the evolution of gamma-ray LF of blazars with main focus on flat spectrum radio quasars (FSRQs). This requires analysis of both gamma-ray and optical data, essential for redshift measurements, and a description of the joint LF. We use a new approach which divides the sample into two sub-samples, each with its own flux limit. We use the Fermi-LAT and GAIA observations, and present results on the gamma-ray LF and its evolution, and determine the intrinsic correlation between the gamma-ray and optical luminosities corrected for the well known false correlation induced by their similar redshift dependence and evolution of the two luminosities. We also present a direct estimation of the contribution of blazars to the spectrum of the extragalactic gamma-ray background.