Poster Presentation

Environments of Quasars and Their Feedback on Nearby Galaxies: Insights from Subaru/HSC Data

Author(s): Yuta Suzuki, Yoshiki Matsuoka (Ehime University), Hisakazu Uchiyama (Hosei University), Jun Toshikawa (NHAO), Satoshi Kikuta, Haruka Kusakabe (University of Tokyo), Masatoshi Imanishi (NAOJ), and et al.

Presenter: Yuta Suzuki (Ehime University)

The emergence of quasars is widely understood within galaxy evolution models, where major mergers between gas-rich galaxies trigger quasar activity. Under this scenario, quasars are expected to reside in high-density regions (like protocluster) where such mergers are more likely. However, strong ultraviolet (UV) radiation from quasars can ionize and heat the surrounding gas, possibly suppressing star formation. This feedback suggests an alternative view, in which quasars may instead be found in low-density environments where galaxy formation is inhibited. Although both scenarios have observational support, limited sample sizes have prevented a unified understanding of quasar environments. To address this issue, we conducted a statistical study using wide-field Subaru
/HSC imaging.
First, we examined the density of Lyman break galaxies (LBGs) around 67 quasars at z~ 3. We found that quasars do not preferentially reside in strongly overdense regions such as protoclusters, but in environments similar to those of field LBGs.
Fainter LBGs were also less abundant near quasars.
Then, we investigated quasar environments at z ~ 2.2 by comparing Lyα emitters (LAEs) selected with narrowband filters to continuum-selected galaxies from broadband data. LAEs showed significantly lower densities around quasars.
These results suggest quasars may form regardless of large-scale environment and later suppress nearby galaxy formation via UV feedback. In this talk, we will present these results in detail.