Weighing obscured and unobscured quasar hosts with the cosmic microwave background

We cross-correlate a cosmic microwave background (CMB) lensing map with the projected space densities of quasars to measure the bias and halo masses of a quasar sample split into obscured and unobscured populations, the first application of this method to distinct quasar subclasses. Several recent studies of the angular clustering of obscured quasars have shown that these objects likely reside in higher mass haloes compared to their unobscured counterparts. This has important implications for models of the structure and geometry of quasars, their role in growing supermassive black holes, and mutual quasar/host galaxy evolution. However, the magnitude and significance of this difference has varied from study to study. Using data from Planck, WISE, and Sloan Digital Sky Survey, we follow up on these results using the independent method of CMB lensing cross-correlations. The region and sample are identical to that used for recent angular clustering measurements, allowing for a direct comparison of the CMB-lensing and angular clustering methods. At z ~ 1, we find that the bias of obscured quasars is b_q = 2.57 ± 0.24, while that of unobscured quasars is bq = 1.89 ± 0.19. This corresponds to halo masses of log(M_h/M_⊙ h^-1) = 13.24^+0.14 _-0.15 (obscured) and log(M_h/M_⊙ h^-1) = 12.71^+0.15 _-0.13 (unobscured). These results agree well with those from angular clustering (well within 1τ), and confirm that obscured quasars reside in host haloes ~3 times as massive as haloes hosting unobscured quasars. This implies that quasars spend a significant portion of their lifetime in an obscured state, possibly more than one-half of the entire active phase.