Detailed Shape and Evolutionary Behavior of the X-ray Luminosity Function of Active Galactic Nuclei

TL;DR

This paper constructs a detailed rest-frame 2-10 keV X-ray luminosity function of AGNs, revealing complex evolution patterns and structural features across redshifts and luminosities, based on extensive multi-survey data.

Contribution

It provides a comprehensive analytical model of the AGN XLF incorporating realistic spectra, absorption, and redshift uncertainties, highlighting two-phase AGN evolution.

Findings

Flattening of the low luminosity slope at z>~0.6

Two breaks in the number density curves indicating two-phase evolution

Revealed detailed AGN downsizing structures

Abstract

We construct the rest-frame 2--10 keV intrinsic X-ray luminosity function of Active Galactic Nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field-South. We use ~3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of the XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. In deriving our XLF, we take into account realistic AGN spectrum templates, absorption corrections, and probability density distributions in photometric redshift. We present an analytical expression for the overall behavior of the XLF in terms of the luminosity-dependent density evolution, smoothed two power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned XLF. We observe a sudden flattening of the low luminosity end slope of the XLF slope at z>~0.6. Detailed structures of the AGN downsizing have been also revealed, where the number density curves have two clear breaks at all luminosity classes above log LX>43. The two break structure is suggestive of two-phase AGN evolution, consisting of major merger triggering and secular processes.