Luminosity Dependent X-ray AGN Clustering ?

TL;DR

This study investigates how the clustering of X-ray selected AGNs varies with flux limit, revealing a luminosity-dependent clustering pattern at redshift around 1, which helps reconcile previous inconsistent results.

Contribution

It demonstrates a flux-limit dependent clustering strength in X-ray AGNs, suggesting luminosity-dependent clustering at z~1, and reconciles previous disparate clustering measurements.

Findings

Clustering strength increases with flux limit.

Clustering lengths are consistent with previous spatial measures.

Evidence for luminosity-dependent clustering at z~1.

Abstract

We have analysed the angular clustering of X-ray selected active galactic nuclei (AGN) in different flux-limited sub-samples of the Chandra Deep Field North (CDF-N) and South (CDF-S) surveys. We find a strong dependence of the clustering strength on the sub-sample flux-limit, a fact which explains most of the disparate clustering results of different XMM and Chandra surveys. Using Limber's equation, we find that the inverted CDF-N and CDF-S spatial clustering lengths are consistent with direct spatial clustering measures found in the literature, while at higher flux-limits the clustering length increases considerably; for example, at $fx,limit ~ 10^{-15} erg/s/cm^{-2} we obtain r_0~ 17 +- 5 and 18+- 3 h^{-1} Mpc, for the CDF-N and CDF-S, respectively. We show that the observed flux-limit clustering trend hints towards an X-ray luminosity dependent clustering of X-ray selected, $z\sim 1$, AGNs.