2025A&A...696A.176I

Context. Hickson Compact Groups (HCGs) are dense gravitationally bound collections of four to ten galaxies and are ideal for studying gas and star formation quenching processes.
Aims. We aim to understand the transition of HCGs from possessing complex H I tidal structures (so-called phase 2 groups) to a phase where galaxies have lost most or all of their H I (phase 3). We also seek to detect diffuse H I gas that was previously missed by the Very Large Array (VLA).
Methods. We observed three phase 2 and three phase 3 HCGs with MeerKAT and reduced the data using the Containerized Automated Radio Astronomy Calibration (CARACal) pipeline. We produced data cubes, moment maps, and integrated spectra, and we compared our findings with previous VLA and Green Bank Telescope observations.
Results. Compared with previous VLA observations, MeerKAT reveals much more extended tidal features in phase 2 and some new high surface brightness features in phase 3 groups. However, no diffuse H I component was found in phase 3 groups. We also detected many surrounding galaxies for both phase 2 and phase 3 groups, most of which are normal disc galaxies.
Conclusions. The difference between phase 2 and phase 3 groups is still substantial, supporting the previous finding that the transition between the two phases must be abrupt.