The Chandra cosmos legacy survey: clustering of X-ray-selected AGNs at 2.9 ≤ z ≤ 5.5 using photometric redshift probability distribution functions

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 ($⟨L_{bol}⟩\sim$ 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.