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The lenticular galaxy ESO 243-49 hosts the ultraluminous X-ray source HLX-1,the best candidate intermediate mass black hole (IMBH) currently known. Theenvironments of IMBHs remain unknown, however the proposed candidates includethe nuclei of dwarf galaxies or globular clusters. Evidence at opticalwavelengths points at HLX-1 being the remnant of an accreted dwarf galaxy. Herewe report the Australia Telescope Compact Array radio observations of HIemission in and around ESO 243-49 searching for signatures of a recent mergerevent. No HI line emission is detected in ESO 243-49 with a 5$\sigma$ upperlimit on the HI gas mass of a few $10^8 M_{\odot}$. A likely reason for thisnon-detection is the cluster environment depleting ESO 243-49's HI gasreservoir. The upper limit is consistent with an interpretation of HLX-1 as adwarf satellite of ESO 243-49, however more sensitive observations are requiredfor a detection. We detect ~$5 \times 10^8 M_{\odot}$ of HI gas in the peculiarspiral galaxy AM 0108-462, located at a projected distance of ~170 kpc from ESO243-49. This amount of HI gas is ~10 times less than in spiral galaxies withsimilar optical and near-infrared properties in the field, strengthening theconclusion that the cluster environment indeed depletes the HI gas reservoir ofthese two galaxies. Here we also report observations of AM 0108-462 in severaloptical and near-infrared bands using the Magellan 6.5 m telescopes, andarchival X-ray and ultraviolet observations with XMM-Newton and Swift. Thesedata combined with the HI line data suggest it is likely that AM 0108-462 isexperiencing a merger event.

HI study of the environment around ESO 243-49, the host galaxy of an intermediate mass black hole