The Chandra COSMOS Legacy Survey: Clustering of X-Ray-selected AGNs at 2.9 ≤ z ≤ 5.5 Using Photometric Redshift Probability Distribution Functions

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}<SUB>{bol</SUB>}> ∼ 10<SUP>46</SUP> erg s<SUP>-1</SUP>) 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 <SUB>max</SUB> = 200 h<SUP>-1</SUP> Mpc with the two-halo term and we derive a bias at z ∼ 3.4 equal to b = {6.6}<SUB>-0.55</SUB><SUP>+0.60</SUP>, which corresponds to a typical mass of the hosting halos of log M <SUB>h</SUB> = {12.83}<SUB>-0.11</SUB><SUP>+0.12</SUP> h<SUP>-1</SUP> M <SUB>☉</SUB>. A similar bias is derived using the redshift-space 2pcf, modeled including the typical phot-z error σ <SUB> z </SUB> = 0.052 of our sample at z ≥ 2.9. Once we integrate the projected 2pcf up to π <SUB>max</SUB> = 200 h<SUP>-1</SUP> 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 <SUB>h</SUB> = {12.92}<SUB>-0.18</SUB><SUP>+0.13</SUP> at z = 2.8 and log M <SUB>h</SUB> = {12.83}<SUB>-0.11</SUB><SUP>+0.12</SUP> 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.