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 gas cloud associated with the asymmetric spiral galaxy NGC 2442. This object, designated HIPASS J0731–69, contains ∼ 10 M⊙ of H I, or nearly one-third as much atomic gas as NGC 2442 itself. No optical counterpart to any part of HIPASS J0731–69 has yet been identified, consistent with the gas being diffuse, and with its stream-like kinematics. If the gas in HIPASS J0731–69 was once part of NGC 2442, then it was most likely a fairly recent tidal encounter with a moderately massive companion which tore it loose, although the possibility of ram-pressure stripping cannot be ruled out. This discovery 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. Subject headings: galaxies: individual (NGC 2442) — galaxies: interactions — radio lines: galaxies