No overdensity of Lyman Alpha Emitting Galaxies around a quasar at z~5.7

TL;DR

This study searches for Lyman Alpha Emitting galaxies around a high-redshift quasar using narrow-band imaging and finds no overdensity, challenging expectations of dense environments around such quasars.

Contribution

It provides the first narrow-band imaging search for LAEs around a z~5.7 quasar, offering new insights into quasar environments at high redshift.

Findings

No overdensity of LAEs detected around the quasar

Possible quasar radiation inhibits nearby galaxy formation

Results suggest quasars may not always reside in dense environments

Abstract

Bright quasars, observed when the Universe was less than one billion years old (z>5.5), are known to host massive black holes (~10$^{9}$ M$_{\odot}$), and are thought to reside in the center of massive dark matter overdensities. In this picture, overdensities of galaxies are expected around high redshift quasars. However, observations based on the detection of Lyman Break Galaxies (LBGs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of LBGs, which are selected through broad-band filters only. To circumvent such uncertainties, we here perform a search for Lyman Alpha Emitting galaxies (LAEs) in the field of the quasar PSO J215.1512-16.0417 at z~5.73, through narrow band, deep imaging with FORS2 at the VLT. We study an area of 37 arcmin$^{2}$, i.e. ~206 comoving Mpc$^{2}$ at the redshift of the quasar. We find no evidence for an overdensity of LAEs in the quasar field with respect to blank field studies. Possible explanations for these findings include that our survey volume is too small, or that the strong ionizing radiation from the quasar hinders galaxy formation in its immediate proximity. Another possibility is that these quasars are not situated in the dense environments predicted by some simulations.