Host Dark Matter Halos of WISE-selected Obscured & Unobscured Quasars: Evidence for Evolution

TL;DR

This study investigates the environments of obscured and unobscured quasars using clustering and lensing measurements, finding that obscured quasars inhabit more massive dark matter halos, supporting an evolutionary model over a simple orientation-based explanation.

Contribution

It provides the first combined analysis of clustering and CMB lensing for a large quasar sample, revealing environmental differences that suggest an evolutionary phase in quasar development.

Findings

Obscured quasars reside in more massive halos (~10^12.9 h^{-1} M_sun) than unobscured ones (~10^12.6 h^{-1} M_sun).

Clustering and lensing results are consistent and robust against redshift uncertainties.

Results challenge models that attribute obscuration solely to orientation effects.

Abstract

Obscuration in quasars may arise from steep viewing angles along the dusty torus, or instead may represent a distinct phase of supermassive black hole growth. We test these scenarios by probing the host dark matter halo environments of $\sim 1.4$ million WISE-selected obscured and unobscured quasars at $\langle z \rangle = 1.4$ using angular clustering measurements as well as cross-correlation measurements of quasar positions with the gravitational lensing of the cosmic microwave background (CMB). We interpret these signals within a halo occupation distribution (HOD) framework to conclude that obscured systems reside in more massive effective halos ($ \sim 10^{12.9} h^{-1} M_{\odot}$) than their unobscured counterparts ($ \sim 10^{12.6} h^{-1} M_{\odot}$), though we do not detect a difference in the satellite fraction. We find excellent agreement between the clustering and lensing analyses and show that this implies the observed difference is robust to uncertainties in the obscured quasar redshift distribution, highlighting the power of combining angular clustering and weak lensing measurements. This finding appears in tension with models that ascribe obscuration exclusively to orientation of the dusty torus along the line-of-sight, and instead may be consistent with the notion that some obscured quasars are attenuated by galaxy-scale or circumnuclear material during an evolutionary phase.