The Clustering of X-Ray Luminous Quasars

Abstract

The clustering of active galactic nuclei (AGN) sheds light on their typical large (Mpc-scale) environments, which can constrain the growth and evolution of supermassive black holes. Here we measure the clustering of luminous X-ray-selected AGN in the Stripe 82X and XMM-XXL-north surveys around the peak epoch of black hole growth, in order to investigate the dependence of luminosity on largescale AGN environment. We compute the auto-correlation function of AGN in two luminosity bins, 10 43 ≤ L X < 10 44.5 erg s −1 at z ∼ 0.8 and L X ≥ 10 44.5 erg s −1 at z ∼ 1.8, and calculate the AGN bias taking into account the redshift distribution of the sources using three different methods. Our results show that while the less luminous sample has an inferred typical halo mass that is smaller than for the more luminous AGN, the host halo mass may be less dependent on luminosity than suggested in previous work. Focusing on the luminous sample, we calculate a typical host halo mass of ∼ 10 13 M h −1 , which is similar to previous measurements of moderate-luminosity X-ray AGN and significantly larger than the values found for optical quasars of similar luminosities and redshifts. We suggest that the clustering differences between different AGN selection techniques are dominated by selection biases, and not due to a dependence on AGN luminosity. We discuss the limitations of inferring AGN triggering mechanisms from halo masses derived by large-scale bias.

Quasars at intermediate redshift are not special; but they are often satellites

“…This is another key result as it immediately explains the lack of dependence on luminosity for QSO clustering (e.g. da Ângela et al 2008;Shen et al 2009Shen et al , 2013Chehade et al 2016;Powell et al 2020). This is consistent with the result that the QSO luminosity possibly has large scatter at fixed black hole mass and hence do not particularly correlates with the host halo mass Hickox et al (2014).…”

The AGN–galaxy–halo connection: the distribution of AGN host halo masses to z = 2.5

“…Our model does not extend to ∼ 0, where the observational data are shown in dark blue. We note in particular the good agreement with the = 1.5 − 2.0 results (from Krishnan et al 2020 andPowell et al 2020, shown in purple in the right panel), which do show a substantial rise in the absolute bias from X ∼ 10 44 − 10 45 erg s −1 . Figure 8.…”

“…Croom et al 2005;Cappelluti et al 2010;Georgakakis et al 2014). Here, we show explicitly that using a measured bias to directly infer a halo mass, without taking into account the satellite fraction or underlying mass distribution, leads to estimates that are systematically offset from the true averages of either the (sub-)halo or parent halo masses (see also DeGraf & Sijacki 2017;Powell et al 2020).…”

The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release

“…While the primary objectives of eBOSS and other SDSS-IV programs informed the target selection for quasars in DR16Q (see Section 2.2), eBOSS quasar catalogs have been used in a number of other recent research studies beyond the eBOSS core programs. These include, but are certainly not limited to, the study of changing-look quasars, which can be used to investigate accretion mechanisms and other quasar physics (Sheng et al 2020); X-ray studies of the clustering of quasars, which can also give insight into the growth and evolution of supermassive black holes (Powell et al 2020); studies of the correlation between X-ray and emission-line luminosities (Timlin et al 2020); studies of quasar outflows in the far-infrared and radio bands via follow-up of optically confirmed quasars (Hall et al 2019); studies of the correlation of outflow velocities with bolometric luminosity in broad absorption-line (BAL) quasars (Bruni et al 2019); and studies of the variability in BAL troughs over time (Grier et al 2016;McGraw et al 2017). To help facilitate these sorts of quasar studies, DR16Q includes multiple redshift estimates, BAL and damped Lyα (DLA) quasar identifications, and compiled multiwavelength data.…”