# The characteristic halo masses of half-a-million WISE-selected quasars

## TL;DR

This study refines measurements of dark matter halo masses for WISE-selected quasars, confirming that obscured quasars inhabit significantly more massive haloes than unobscured ones, supporting an environmental or evolutionary link to obscuration.

## Contribution

It expands the survey area and improves measurement precision, confirming the halo mass difference between obscured and unobscured quasars using multiple techniques.

## Key findings

- Obscured quasars reside in haloes three times more massive than unobscured quasars.
- The halo mass difference is statistically significant at about 5 sigma.
- Obscured and unobscured quasars are well-matched in redshift and luminosity, supporting intrinsic differences.

## Abstract

Recent work has found evidence for a difference in the bias and dark matter halo masses of WISE-selected obscured and unobscured quasars, implying a distinction between these populations beyond random line-of-sight effects. However, the significance of this difference in the most up-to-date measurements is relatively weak, at $\sim$2$\sigma$ for individual measurements but bolstered by agreement from different techniques, including angular clustering and cross-correlations with cosmic microwave background (CMB) lensing maps. Here, we expand the footprint of previous work, aiming to improve the precision of both methods. In this larger area we correct for position dependent selection effects, in particular fluctuations of the WISE-selected quasar density as a function of Galactic latitude. We also measure the cross-correlation of the obscured and unobscured samples and confirm that they are well-matched in redshift, both centred at $z=1$. Combined with very similar detection fractions and magnitude distributions in the long-wavelength WISE bands, this redshift match strongly supports the fact that IR selection identifies obscured and unobscured quasars of similar bolometric luminosity. Finally, we perform cross-correlations with confirmed spectroscopic quasars, again confirming the results from other methods --- obscured quasars reside in haloes a factor of 3 times more massive than unobscured quasars. This difference is significant at the $\sim$5$\sigma$ level when the measurements are combined, strong support for the idea that obscuration in at least some quasars is tied to the larger environment, and may have an evolutionary component.