X-ray selected AGNs: The Clustering Properties

Abstract

Clustering properties of two samples of X-ray selected AGNs are compared with IR/Optical galactic samples. These are the Einstein Observatory Extended Medium Sensitivity Survey: EMSS; and a sample of 654 ROSAT detected radio quasars. The cosmological dipole moment is calculated for these samples, yielding the values of $b \Omega_o^{-0.6}$. We find this factor to be $0.68 \pm 0.22$ for the EMSS sample, and $1.02 \pm 0.014$ for the quasars sample. Comparing these values with that of the IRAS 1.2 Jy sample $(1.95 \pm 0.096)$, suggests that these AGNs are less clustered than the IRAS galaxies. For each sample there is a depth at which the amplitude of the dipole growth curve saturates. This convergence radius $(R_{conv})$ is found to be $\sim 300-400$ h$^{-1}$ Mpc for the EMSS sample and $\sim 450-500$ h$^{-1}$ Mpc for the ROSAT detected quasars sample, which suggests that X-ray AGNs have a much deeper contribution to the Local Group (LG) motion compared to the galaxy and cluster samples. Using the properties of the angular and spatial correlation functions for these samples, we find: $b_{IRAS}/b_{quasars} = 3.61 \pm 2.7$; $b_{IRAS}/b_{EMSS}= 8.46 \pm 6.4$ and $b_{quasars} / b_{EMSS} = 2.35 \pm 0.2$. Using Chi-squared minimisation, we have fitted the angular correlation functions using the standard power law model of the form: $W(\theta)= A \theta^{-\delta}$, and the spatial correlation functions using the power law model of the form: $\xi(r) =(r/r_{0})^{-\gamma}$. For the angular correlation functions, we find $A \sim0.6$ for the AGN auto-correlations and $A \sim0.2-0.3$ for the AGN-IRAS galaxy cross-correlations. Also $\delta$ is found to be $~ 0.8-1.1$. In the spatial correlation analysis, we find $r_{o}\sim3.5-5.1$ $h^{-1}Mpc$ and $\gamma\sim1.4-1.7$ .