HI absorption associated with Norma's brightest cluster galaxy

ESO 137-G006 is the brightest cluster galaxy (BCG) of the cool-core and dynamically young Norma cluster. We discover an atomic hydrogen (HI) absorption line associated with this BCG using the Australia Telescope Compact Array. We estimate a gas column density of $\approx (1.3\pm 0.2)\times {10}^{20}{T}_{\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n}}$ atoms cm${}^{-2}$ with spin temperature, $T_{\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n}}\le 194$ K, consistent with the HI properties of other early-type galaxies and cool-core cluster BCGs. The relationship between the presence of cold gas and a cluster cooling flow is unclear. Our results support the scenario that ESO 137-G006 may be a recent arrival to the cluster centre and not the original BCG. This scenario is consistent with the observed spatial alignment of the BCG’s wide-angle tail radio lobes with Norma’s X-ray sub-cluster and the significant line-of-sight velocity offset between the mean velocity of Norma and that of the BCG.