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

Authors:
  • AOA. Oklopcic
    A. Oklopcic
  • VSV. Smolcic
    V. Smolcic
  • SGS. Giodini
    S. Giodini
  • GZG. Zamorani
    G. Zamorani
  • LBL. Birzan
    L. Birzan
  • ESE. Schinnerer
    E. Schinnerer
  • CCC. L. Carilli
    C. L. Carilli
  • AFA. Finoguenov
    A. Finoguenov
  • SLS. Lilly
    S. Lilly
  • AKA. Koekemoer
    A. Koekemoer
  • NSN. Z. Scoville
    N. Z. Scoville
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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.