MeerKAT view of Hickson Compact Groups. II. Deficiency in the core andsurrounding regions

Abstract

Abstract

Context. Hickson compact groups (HCGs) offer an ideal environment for investigating galaxy transformation as a result of interactions. It has been established that the evolutionary sequence of HCGs is marked by an intermediate stage characterised by a substantial amount of H I in their intragroup medium (IGrM) in the form of tidal tails and bridges (phase 2), rapidly followed by a final stage in which no IGrM gas is found and i which their member galaxies are highly H I deficient (phase 3).

Aims. Despite numerous single-dish and interferometric H I studies on the HCGs, a clear H I picture of the groups within their large-scale environment still remains to be uncovered. Taking advantage of MeerKAT’s high column density sensitivity and large field of view, we aim to investigate the rapid transformation of HCGs from the intermediate to late phases, and establish a picture of their gas content variations in the context of their large-scale environments.

Methods. We performed MeerKAT observations of six HCGs that were selected to represent the intermediate and late phases of the proposed evolutionary sequence. Combining the H I observations with data from recent wide-field optical surveys, we evaluated the H I deficiencies of galaxies in a ∼30′ radius of the HCGs.

Results. We find that galaxies surrounding both phases exhibit similar distributions in their gas content. Similarly, galaxies making up the cores of phase 2 HCGs are comparable to their neighbours in terms of H I deficiencies. However, phase 3 groups are over an order of magnitude more deficient than their surroundings, supporting previous findings that late-phase HCG galaxies are more evolved than their large-scale environments.