Understanding the relationship between galaxies hosting active galactic nuclei ( AGN ) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated .
Previous efforts have relied on simple halo mass estimates inferred from clustering , weak gravitational lensing , or halo occupation distribution modeling .
In practice , these approaches remain uncertain because AGN , no matter how they are identified , potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known .
In this work , we show that better constraints can be achieved through a rigorous comparison of the clustering , lensing , and cross-correlation signals of AGN hosts to the fiducial stellar-to-halo mass relation ( SHMR ) derived for all galaxies , irrespective of nuclear activity .
Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone .
Using 382 moderate luminosity X-ray AGN at z < 1 from the COSMOS field , we report the first measurements of weak gravitational lensing from an X-ray selected sample .
Comparing this signal to predictions from the global SHMR , we find that , contrary to previous results , most X-ray AGN do not live in medium size groups —nearly half reside in relatively low mass halos with M _ { 200 b } \sim 10 ^ { 12.5 } M _ { \odot } .
The AGN occupation function is well described by the same form derived for all galaxies but with a lower normalization—the fraction of halos with AGN in our sample is a few percent .
The number of AGN satellite galaxies scales as a power law with host halo mass with a power-law index \alpha = 1 .
By highlighting the relatively “ normal ” way in which moderate luminosity X-ray AGN hosts occupy halos , our results suggest that the environmental signature of distinct fueling modes for luminous QSOs compared to moderate luminosity X-ray AGN is less obvious than previously claimed .