Hipass detection of an intergalactic gas cloud in the NGC 2442 group

We report the discovery from the H I Parkes All-Sky Survey (HIPASS) of a ga s cloud associated with the asymmetric spiral galaxy NGC 2442. This object, designated HIPASS J0731-69, contains similar to 10(9) M-. of H I, or nearl y one-third as much atomic gas as NGC 2442 itself. No optical counterpart t o any part of HIPASS J0731-69 has yet been identified, consistent with the gas being diffuse and its streamlike kinematics. If the gas in HIPASS J0731 -69 was once part of NGC 2442, then it was most likely a fairly recent tida l encounter with a moderately massive companion that tore it loose, althoug h the possibility of ram-pressure stripping cannot be ruled out. This disco very highlights the potential of the HIPASS data for yielding new clues to the nature of some of the best-known galaxies in the local universe.