THE CHANDRA COSMOS LEGACY SURVEY: CLUSTERING OF X-RAY-SELECTED AGNs AT 2.9 ≤ z ≤ 5.5 USING PHOTOMETRIC REDSHIFT PROBABILITY DISTRIBUTION FUNCTIONS

Abstract

ABSTRACT We present the measurement of the projected and redshift-space two-point correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy active galactic nucleus (AGN) at 2.9 ≤ z ≤ 5.5 ( 〈 L bol 〉 ∼ 1046 erg s−1) using the generalized clustering estimator based on phot-z probability distribution functions in addition to any available spec-z. We model the projected 2pcf, estimated using π max = 200 h−1 Mpc with the two-halo term and we derive a bias at z ∼ 3.4 equal to b = 6.6 − 0.55 + 0.60 , which corresponds to a typical mass of the hosting halos of log M h = 12.83 − 0.11 + 0.12 h−1 M ⊙. A similar bias is derived using the redshift-space 2pcf, modeled including the typical phot-z error σ z = 0.052 of our sample at z ≥ 2.9. Once we integrate the projected 2pcf up to π max = 200 h−1 Mpc, the bias of XMM and Chandra COSMOS at z = 2.8 used in Allevato et al. is consistent with our results at higher redshifts. The results suggest only a slight increase of the bias factor of COSMOS AGNs at z ≳ 3 with the typical hosting halo mass of moderate-luminosity AGNs almost constant with redshift and equal to log M h = 12.92 − 0.18 + 0.13 at z = 2.8 and log M h = 12.83 − 0.11 + 0.12 at z ∼ 3.4, respectively. The observed redshift evolution of the bias of COSMOS AGNs implies that moderate-luminosity AGNs still inhabit group-sized halos at z ≳ 3, but slightly less massive than observed in different independent studies using X-ray AGNs at z ≤ 2.