Cross-correlation of Luminous Red Galaxies with ML-selected AGN in HSC-SSP III: HOD Parameters for Type I and Type II Quasars

Abstract

Understanding the dark matter (DM) halo environment in which galaxies that host active galactic nuclei (AGN) reside is a window into the nature of supermassive black hole (SMBH) accretion. We apply halo occupation distribution (HOD) modeling tools to interpret the angular cross-correlation functions between $1.5\times 10^6$ luminous red galaxies (LRGs) and our $\sim 28,500$ Hyper Suprime-Cam + Wide-field Infrared Survey Explorer-selected (and $L_{6\mu m}$-limited) AGN to infer the halo properties of distinct quasar samples at physical scales $s>0.1\mathrm{Mpc}$, for $z\in 0.7-1.0$. We find that Type I (unobscured) and Type II (obscured) AGN cluster differently, both on small and large physical scales. The derived HODs imply that Type I AGN reside, on average, in substantially ($\sim 3\times$) more massive halos ($M_h\sim 10^{13.4}{M}_{\odot }$) than Type II AGN ($M_h\sim 10^{12.9}{M}_{\odot }$) at $>5\sigma$ significance. While Type II AGN show one-halo correlations similar to that of galaxies of their average halo mass, the Type I AGN intra-halo clustering signal is significantly shallower. We interpret this observation with HOD methods and find Type I AGN are significantly less likely ($f_{sat}\sim 0.05_{-0.05}^{+1}\%$) to be found in satellite galaxies than Type II AGN. We find reddened + obscured AGN to have typical satellite fractions for their inferred average halo mass ($\sim 10^{13}{M}_{\odot }$), with $f_{sat}\sim 20_{-5}^{+10}\%$. Taken together, these results pose a significant challenge to the strict unified AGN morphological model, and instead suggest that a quasar's spectral class is strongly correlated with its host galaxy's dark matter halo environment. These intriguing results have provided a more complex picture of the SMBH -- DM halo connection, and motivate future analyses of the intrinsic galaxy and accretion properties of AGN.

28 pages, 12 figures, submitted to ApJ