Clustering of galaxies around AGN in the HSC Wide survey

TL;DR

This study investigates the clustering of galaxies around AGNs across a wide redshift range, revealing dependencies on galaxy brightness and color, and exploring the relationship between SMBH mass and galaxy environment.

Contribution

It provides new insights into the large-scale environments of AGNs and their evolution, using extensive SDSS and HSC survey data to analyze galaxy clustering around SMBHs.

Findings

Cross-correlation length increases with galaxy brightness at low redshift.

No significant correlation between SMBH mass and galaxy clustering for blue galaxies.

Indication of SMBH mass dependence in red galaxy clustering.

Abstract

We have measured the clustering of galaxies around active galactic nuclei (AGN) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the relation between the large scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from 240~deg$^{2}$ S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0.6--3.0, and the masses of the SMBHs lie in the range $10^{7.5}$--$10^{10}$~M$_{\odot}$. The absolute magnitude of the galaxy samples reaches to $M_{\lambda 310}$ $\sim$ $-$18 at rest frame wavelength 310~nm for the low-redshift end of the samples. More than 70\% of the galaxies in the analysis are blue. We found a significant dependence of the cross-correlation length on redshift, which primarily reflects the brightness dependence of the galaxy clustering. At the lowest redshifts the cross-correlation length increases from 7~$h^{-1}$~Mpc around $M_{\lambda 310}$$ = $$-19$~mag to $>$10~$h^{-1}$~Mpc beyond $M_{\lambda 310}$$ = $$-20$~mag. No significant dependence of the cross-correlation length on BH mass was found for whole galaxy samples dominated by blue galaxies, while there was an indication of BH mass dependence in the cross-correlation with red galaxies. These results provides a picture of the environment of AGNs studied in this paper being enriched with blue starforming galaxies, and a fraction of the galaxies are being evolved to red galaxies along with the evolution of SMBHs in that system.