Environments around quasars at $z\sim$3 revealed by wide-field imaging with Subaru HSC and CFHT

TL;DR

This study investigates the environments of quasars at redshift ~3 using wide-field imaging data, revealing their typical halo masses, lack of correlation with galaxy properties, and potential UV radiation effects on nearby galaxy formation.

Contribution

It provides the first large-scale analysis of quasar environments at z~3 combining Subaru HSC and CFHT data, and explores the impact of quasar UV radiation on surrounding galaxy formation.

Findings

Quasars have similar surrounding density distributions as U-dropout galaxies.

Three quasars are associated with protocluster candidates.

No significant correlation between local overdensity and quasar properties.

Abstract

We examine the local density environments around 67 quasars at $z\sim3$, by combining the imaging data of Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) and Canada-France-Hawaii Telescope Large Area U-band Survey (CLAUDS) over about 20 deg$^{2}$. Our measurements exploit $U$-dropout galaxies in the vicinities of quasars taken from Sloan Digital Sky Survey (SDSS). We find that the quasars have the indistinguishable surrounding density distribution from the $U$-dropout galaxies, and that three quasars are associated with protocluster candidates within a projected separation of 3 arcmin. According to a halo evolutionary model, our results suggest that quasars at this epoch occupy haloes with a typical mass of $1.3^{+1.4}_{-0.9} \times 10^{13} h^{-1} \mathrm{M_{\odot}}$. We also investigate the dependence of the local galaxy overdensity on ultraviolet (UV) luminosities, black hole (BH) masses, and proximity zone sizes of the quasars, but no statistically-significant correlation was found. Finally, we find that the local density of faint $U$-dropout galaxies are lower than that of bright $U$-dropout galaxies within a projected distance of $0.51\pm0.05$ physical Mpc, where the quasar UV radiation is 30 times intenser than backgroung UV radiation. We argue that photoevaporation may suppress galaxy formation at short distances where the quasar UV intensity is strong, even in massive haloes.