Quasar Negative Feedback to Surrounding Galaxies Probed with Ly$\alpha$ Emitters and Continuum-Selected Galaxies

TL;DR

This study investigates how quasars at redshift ~2.2 suppress nearby galaxy formation, especially affecting Ly$ extalpha$ Emitters, through statistical analysis of galaxy densities around quasars using deep imaging surveys.

Contribution

It provides the first statistical evidence that quasar photoevaporation reduces galaxy densities, especially for small dark matter haloes hosting Ly$ extalpha$ Emitters, at high redshift.

Findings

LAE density is over 5 sigma lower near quasars compared to continuum galaxies.

High EW LAEs are less dense than low EW LAEs within quasar proximity.

Galaxy densities decrease as they are closer to quasars.

Abstract

We report on the statistical analysis of quasar photoevaporation at $z\sim2.2$ by comparing the density of surrounding Ly$\alpha$ Emitters (LAEs) and continuum-selected galaxies, based on the imaging data of Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) and CFHT Large Area $U$-band Deep Survey (CLAUDS). We select 18 quasars from Sloan Digital Sky Survey (SDSS) in the HSC Deep/UltraDeep fields, normalize the LAE/continuum-selected galaxy distribution around each quasar with the quasar proximity size, stack them, and then measure the average densities of the galaxies. As a result, we find that the density of LAEs is $\gtrsim 5 \sigma$ lower than that of continuum-selected galaxies within the quasar proximity region. Within the quasar proximity region, we find that the LAEs with high Ly$\alpha$ equivalent widths (EWs) are less dense than those with low EWs at the 3$\sigma$ level and that LAEs with EW of $\gtrsim150$ \AA (rest-frame) are predominantly scarce. Finally, we find that both LAEs and continuum-selected galaxies have smaller densities when they are closer to quasars. We argue that the photoevaporation effect is more effective for smaller dark matter haloes predominantly hosting LAEs, but that it may also affect larger haloes.