Title:    Clustering of Broad-line X-ray AGNs from RASS-SDSS 

Takamitsu Miyaji

Observatorio Astronomico NAcional, San Pedro MArtir, UNAMM

Abstract: 

Being unaffected by contamination by stellar components, X-ray survey
is one of the most efficient ways in finding Active Galactic Nuclei
(AGNs) in a comprehensive (albeit not exhaustive) manner and thus
provides us with a good samples of AGNs to investigate their
clustering properties. Investigating clustering properties of AGNs in
various redshift and luminosities gives an observational probe to
understanding the evolution of supermassive black holes (SBMH), as a
complement to investigating, e.g. AGN luminosity functions.

 In this seminar, we present the results of our recent studies on
clustering properties of low redshift broad-line AGNs selected from
the catalog of ROSAT all-sky survey AGNs cross-matched with the Sloan
Digital Sky Survey by Anderson et al. (2007). In our analysis, we have
taken advantage of the sample of Luminous Red Galaxies (LRG) defined
by Eisenstein et al.  in the SDSS area, the auto-correlation function
and the Halo Occupation Distribution (HOD) of which have been
extensively investigated. Our approach is to utilize the
cross-correlation function between the LRGs and the AGNs in the
overlapped redshift range (0.16<z<0.36). We then derived the inferred
AGN auto-correlation function from the measured AGN-LRG CCF and LRG
ACF.  Applying the bias versus dark matter halo mass relation, we find
that those broad-line AGNs (<log Lx> \approx 44) reside in dark matter
halos with a typical mass of ~12.6h^{-1} Msun.  By dividing the AGN
sample into two X-ray luminosity bins and we find that luminous AGNs
are more strongly clustered (higher bias parameter) than lower
luminosity ones.

 We have further attempted to apply the Halo Occupation Distribution
(HOD) modeling to the CCF results, where we use the fixed HODs of LRGs
and parameterized model HOD of the AGNs to fit the CCF. We present the
preliminary results of our HOD analysis as well.