Extended radio AGN at z ~ 1 in the ORELSE survey: The confining effect of dense environments

TL;DR

This study investigates how dense environments, like galaxy clusters, influence the morphology of extended radio AGN at redshifts around 1, finding that dense regions confine radio jets, making them more compact.

Contribution

It provides observational evidence that dense intracluster gas significantly constrains the size of radio jets in ERAGN at z~1, highlighting environmental effects on AGN morphology.

Findings

ERAGN are more compact in high-density environments with 4.5σ significance.

Radio power correlates positively with spatial extent of ERAGN.

Most high-density ERAGN are located in cluster/group environments.

Abstract

Recent hydrodynamic simulations and observations of radio jets have shown that the surrounding environment has a large effect on their resulting morphology. To investigate this we use a sample of 50 Extended Radio Active Galactic Nuclei (ERAGN) detected in the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. These sources are all successfully cross-identified to galaxies within a redshift range of $0.55 \leq z \leq 1.35$, either through spectroscopic redshifts or accurate photometric redshifts. We find that ERAGN are more compact in high-density environments than those in low-density environments at a significance level of 4.5$\sigma$. Among a series of internal properties under our scrutiny, only the radio power demonstrates a positive correlation with their spatial extent. After removing the possible radio power effect, the difference of size in low- and high-density environments persists. In the global environment analyses, the majority (86\%) of high-density ERAGN reside in the cluster/group environment. In addition, ERAGN in the cluster/group central regions are preferentially compact with a small scatter in size, compared to those in the cluster/group intermediate regions and fields. In conclusion, our data appear to support the interpretation that the dense intracluster gas in the central regions of galaxy clusters plays a major role in confining the spatial extent of radio jets.