The Spatial Clustering of ROSAT All-Sky Survey AGNs III. Expanded Sample and Comparison with Optical AGNs

TL;DR

This study investigates the clustering properties of various types of AGNs from the ROSAT and SDSS surveys across a broader redshift range, finding similar clustering behaviors among different AGN classes and confirming weak luminosity dependence.

Contribution

It extends previous clustering analyses of AGNs to higher redshifts and compares X-ray and optical AGNs, revealing consistent clustering properties and halo masses.

Findings

No significant clustering difference between X-ray and optical broad-line AGNs.

Radio-detected AGNs do not show different clustering from non-radio AGNs.

Weak dependence of clustering strength on X-ray luminosity at ~2 sigma.

Abstract

This is the third paper in a series that reports on our investigation of the clustering properties of AGNs identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this paper, we extend the redshift range to 0.07<z<0.50 and measure the clustering amplitudes of both X-ray and optically-selected SDSS broad-line AGNs with and without radio detections as well as for X-ray selected narrow-line RASS/SDSS AGNs. We measure the clustering amplitude through cross-correlation functions (CCFs) with SDSS galaxies and derive the bias by applying a halo occupation distribution (HOD) model directly to the CCFs. We find no statistically convincing difference in the clustering of X-ray and optically-selected broad-line AGNs, as well as with samples in which radio-detected AGNs are excluded. This is in contrast to low redshift optically-selected narrow-line AGNs, where radio-loud AGNs are found in more massive halos than optical AGNs without a radio-detection. The typical dark matter halo masses of our broad-line AGNs are log M_DMH/[h^(-1) M_SUN] ~ 12.4-13.4, consistent with the halo mass range of typical non-AGN galaxies at low redshifts. We find no significant difference between the clustering of X-ray selected narrow-line AGNs and broad-line AGNs. We confirm the weak dependence of the clustering strength on AGN X-ray luminosity at a ~2 sigma level. Finally, we summarize the current picture of AGN clustering to z~1.5 based on three dimensional clustering measurements.