The Swift/BAT AGN Spectroscopic Survey. IX. The Clustering Environments of an Unbiased Sample of Local AGNs

Abstract

We characterize the environments of local accreting supermassive black holes by measuring the clustering of AGN in the Swift/BAT Spectroscopic Survey (BASS). With 548 AGN in the redshift range 0.01 < z < 0.1 over the full sky from the DR1 catalog, BASS provides the largest, least biased sample of local AGN to date due to its hard X-ray selection (14-195 keV) and rich multiwavelength/ancillary data. By measuring the projected cross-correlation function between the AGN and 2MASS galaxies, and interpreting it via halo occupation distribution and subhalo-based models, we constrain the occupation statistics of the full sample, as well as in bins of absorbing column density and black hole mass. We find that AGN tend to reside in galaxy group environments, in agreement with previous studies of AGN throughout a large range of luminosity and redshift, and that on average they occupy their dark matter halos similar to inactive galaxies of comparable stellar mass. We also find evidence that obscured AGN tend to reside in denser environments than unobscured AGN, even when samples were matched in luminosity, redshift, stellar mass, and Eddington ratio. We show that this can be explained either by significantly different halo occupation distributions or statistically different host halo assembly histories. Lastly, we see that massive black holes are slightly more likely to reside in central galaxies than black holes of smaller mass.

The clustering of X-ray AGN at 0.5 &lt; z &lt; 4.5: host galaxies dictate dark matter halo mass

“…For example, at z ∼ 0.7, Mendez et al (2016) find significant differences in the clustering measurements of X-ray, mid-IR and radio AGN, and that these differences are driven by differences in host galaxy properties (such as stellar mass and star-formation rate). Furthermore, at z < 0.1, Powell et al (2018) find that, when accounting for host galaxy properties, AGN occupy dark matter halos consistent with the overall inactive galaxy population.…”

“…The 2pcf of quasars has been studied extensively in the literature and are found to reside in 10 12−12.7 M ⊙ halos out to z ∼ 4 (Croom et al 2005;Shen et al 2007;Ross et al 2009;Eftekharzadeh et al 2015;Ikeda et al 2015;García-Vergara et al 2017). Similarly, lower-luminosity broad line AGN out to z ∼ 0.5 are hosted by dark matter halos of 10 13 M ⊙ (Miyaji et al 2011;Krumpe et al 2012), and X-ray AGN across a wide range of redshifts (z ∼ 0.05, z ∼ 0.1, z ∼ 0.98, z ∼ 1.25, z ∼ 3.4) inhabit halos of ∼ 10 13 M ⊙ (Powell et al 2018;Mountrichas & Georgakakis 2012;Koutoulidis et al 2013;Bradshaw et al 2011;Allevato et al 2016, respectively). Many of these studies interpret the 10 12−13 M ⊙ halo mass as evidence that groups are the ideal environment in which AGN are triggered through galaxy-galaxy interactions (e.g., Miyaji et al 2011;Ikeda et al 2015).…”

The role of galaxy mass on AGN emission: a view from the VANDELS survey

“…The same also seems to be true for X-ray emitting AGN, although in this latter case there is a less general consensus, with values for the typical dark matter halos possibly dependent on obscuration (e.g. Hickox et al 2009;DiPompeo et al 2017;Powell et al 2018). On the other hand, optical and infrared-bright AGN are largely found in relatively smaller galaxies and haloes (e.g.…”

The Clustering of X-Ray Luminous Quasars

“…Studies of black hole halo occupation in hydrodynamic simulations agree (DeGraf & Sijacki 2017). If this is the case, then the typical halo mass obtained from the bias may not represent the median halo mass hosting the AGN population due to incompleteness of the sample (DeGraf & Sijacki 2017;Powell et al 2018). Therefore, we caution against inferences made from host halo mass estimates derived from clustering bias.…”