Molecular gas in radio galaxies at $z=0.4-2.6$ in (proto-)cluster environment

TL;DR

This study explores how dense cluster environments influence molecular gas in radio galaxies at redshifts 0.4 to 2.6, including a tentative detection of CO emission in a high-redshift BCG candidate.

Contribution

First investigation of molecular gas in radio galaxies within dense environments at high redshift, including the most distant BCG candidate detected in CO.

Findings

Tentative CO(7→6) detection in a $z=2.63$ BCG candidate

Cluster environment may inhibit gas refueling mechanisms

Radio galaxies are promising targets for future telescopes

Abstract

We investigate the role of the environment in processing molecular gas in radio galaxies (RGs). We observed five RGs at $z=0.4-2.6$ in dense Mpc-scale environment with the IRAM-30m telescope. We set four upper-limits and report a tentative CO(7$\rightarrow$6) detection for COSMOS-FRI 70 at $z=2.63$, which is the most distant brightest cluster galaxy (BCG) candidate detected in CO. We speculate that the cluster environment might have played a role in preventing the refueling via environmental mechanisms such as galaxy harassment, strangulation, ram-pressure, or tidal stripping. The RGs of this work are excellent targets for ALMA as well as next generation telescopes such as the James Webb Space Telescope.