The VLA H I Observations of Stephan's Quintet (HCG 92)

Using the Very Large Array, we have made spectral-line and continuum observations of the neutral hydrogen in the direction of the compact group of galaxies Stephan's Quintet. The high-velocity clouds between 5600 and 6600 km s^-1, the disk of the foreground galaxy NGC 7320 at 800 km s^-1, the extended continuum ridge near the center of the group, and three faint dwarflike galaxies in the surrounding field were imaged with the C, CS, and D configurations. Four of the H I clouds previously detected are confirmed. The two largest H I features are coincident with and concentrated mainly along separate large tidal tails that extend eastward. The most diffuse of the four clouds is resolved into two clumps, one coinciding with tidal features south of NGC 7318A and the other devoid of any detectable stellar or Hα sources. The two compact clouds along the same line of sight have peak emission at luminous infrared and bright Hα sources probably indicative of star-forming activity. The total amount of H I detected at high redshifts is ~10¹⁰M_solar. As in previous H I studies of the group, no detectable emission was measured at the positions of any high-redshift galaxies, so that any H I still bound to their disks must be less than 2.4×10⁷ M_solar. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.