The Properties of Radio Galaxies and the Effect of Environment in Large Scale Structures at $z\sim1$

TL;DR

This study analyzes the properties and environmental preferences of 89 spectroscopically-confirmed radio galaxies at redshifts 0.65 to 0.96 within large scale structures, classifying them into AGN, hybrid, and star-forming types.

Contribution

It introduces a detailed classification of radio galaxies at z~1 and explores their environmental dependencies, revealing distinct behaviors of each subclass.

Findings

AGN are in dense environments and cluster cores.

Star-forming galaxies prefer intermediate-density environments.

Hybrids are a distinct population dominated by HERGs.

Abstract

In this study we investigate 89 radio galaxies that are spectroscopically-confirmed to be members of five large scale structures in the redshift range of $0.65 \le z \le 0.96$. Based on a two-stage classification scheme, the radio galaxies are classified into three sub-classes: active galactic nucleus (AGN), hybrid, and star-forming galaxy (SFG). We study the properties of the three radio sub-classes and their global and local environmental preferences. We find AGN hosts are the most massive population and exhibit quiescence in their star-formation activity. The SFG population has a comparable stellar mass to those hosting a radio AGN but are unequivocally powered by star formation. Hybrids, though selected as an intermediate population in our classification scheme, were found in almost all analyses to be a unique type of radio galaxies rather than a mixture of AGN and SFGs. They are dominated by a high-excitation radio galaxy (HERG) population. We discuss environmental effects and scenarios for each sub-class. AGN tend to be preferentially located in locally dense environments and in the cores of clusters/groups, with these preferences persisting when comparing to galaxies of similar colour and stellar mass, suggesting that their activity may be ignited in the cluster/group virialized core regions. Conversely, SFGs exhibit a strong preference for intermediate-density global environments, suggesting that dusty starbursting activity in LSSs is largely driven by galaxy-galaxy interactions and merging.