Identifying dynamically young galaxy groups via wide-angle tail galaxies: A case study in the COSMOS field at z=0.53

TL;DR

This study uses a wide-angle tail radio galaxy in the COSMOS field at z=0.53 to identify a dynamically young galaxy group undergoing a merger, highlighting the role of radio-AGN in influencing baryon content.

Contribution

It demonstrates that wide-angle tail galaxies can serve as indicators of dynamically young, unrelaxed galaxy groups and explores their impact on baryon expulsion.

Findings

CWAT-02's host galaxy is the brightest in the group but offset from the center of mass.

Velocity estimates suggest the group is dynamically young and merging.

Radio-AGN heating may contribute to baryon expulsion from galaxy groups.

Abstract

We present an analysis of a wide-angle tail (WAT) radio galaxy located in a galaxy group in the COSMOS field at a redshift of z=0.53 (hereafter CWAT-02). We find that the host galaxy of CWAT-02 is the brightest galaxy in the group, although it does not coincide with the center of mass of the system. Estimating a) the velocity of CWAT-02, relative to the intra-cluster medium (ICM), and b) the line-of-sight peculiar velocity of CWAT-02's host galaxy, relative to the average velocity of the group, we find that both values are higher than those expected for a dominant galaxy in a relaxed system. This suggests that CWAT-02's host group is dynamically young and likely in the process of an ongoing group merger. Our results are consistent with previous findings showing that the presence of a wide-angle tail galaxy in a galaxy group or cluster can be used as an indicator of dynamically young non-relaxed systems. Taking the unrelaxed state of CWAT-02's host group into account, we discuss the impact of radio-AGN heating from CWAT-02 onto its environment, in the context of the missing baryon problem in galaxy groups. Our analysis strengthens recent results suggesting that radio-AGN heating may be powerful enough to expel baryons from galaxy groups.