2022MNRAS.511..980S

We present H I and radio continuum, narrow-band Hα imaging, IFU spectroscopy, and X-ray observations of the FGC 1287 triplet projected ∼1.8 Mpc west of the galaxy cluster Abell 1367. One triplet member, FGC 1287, displays an exceptionally long, 250 kpc H I tail and an unperturbed stellar disc which are the typical signatures of ram pressure stripping (RPS). To generate detectable RPS signatures the presence of an Intracluster medium ICM or intragroup medium IGM with sufficient density to produce RPS at a realistic velocity relative to the ICM or IGM is a prerequisite. However, XMM-Newton observations were not able to detect X-ray emission from the triplet, implying that if a hot ICM/IGM is present, its density, n_e, is less than 2.6 x 10^–5 cm^–3. Higher resolution VLA H I data presented here show FGC 1287's H I disc is truncated and significantly warped, whereas the H I tail is clumpy. TNG Hα imaging identified three star-forming clumps projected within 20 kpc of FGC 1287's disc, with VIMOS-IFU data confirming two of these are counterparts to H I clumps in the tail. The triplet's H I kinematics, together with Hα and radio continuum imaging suggests an interaction may have enhanced star formation in FGC 1287's disc, but cannot readily account for the origin of the long H I tail. We consider several scenarios which might reconcile RPS with the non-detection of ICM or IGM X-ray emission but none of these unambiguously explains the origin of the long H I tail.