A galaxy populations study of a radio-selected protocluster at z~3.1

TL;DR

This study investigates galaxy populations in a z~3.1 protocluster, revealing an overdensity of Lyman break galaxies near a radio galaxy, with similar properties to field galaxies, indicating early-stage formation.

Contribution

It provides the first detailed multi-galaxy population analysis of this specific high-redshift protocluster, combining various selection techniques and SED fitting.

Findings

Overdensity of Lyman break galaxies near the radio galaxy

No significant overdensity of Balmer break galaxies detected

Galaxies with highest masses and star formation rates are near the radio galaxy

Abstract

We present a population study of several types of galaxies within the protocluster surrounding the radio galaxy MRC0316-257 at z~3.1. In addition to the known population of Ly_alpha emitters (LAEs) and [OIII] emitters, we use colour selection techniques to identify protocluster candidates that are Lyman break galaxies (LBG) and Balmer break galaxies (BBGs). The radio galaxy field contains an excess of LBG candidates, with a surface density 1.6\pm0.3 times larger than found for comparable blank fields. This surface overdensity corresponds to an LBG volume overdensity of ~8\pm4. The BBG photometric redshift distribution peaks at the protocluster's redshift, but we detect no significant surface overdensity of BBG. This is not surprising because a volume overdensity similar to the LBGs would have resulted in a surface density of ~1.2 that found in the blank field. This could not have been detected in our sample. Masses and star formation rates of the candidate protocluster galaxies are determined using SED fitting. These properties are not significantly different from those of field galaxies. The galaxies with the highest masses and star formation rates are located near the radio galaxy, indicating that the protocluster environment influences galaxy evolution at z~3. We conclude that the protocluster around MRC0316-257 is still in the early stages of formation.