The VLA H [CSC]i[/CSC] Observations of Stephan’s Quintet (HCG 92)

Abstract

Using the VLA, 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, the disk of the foreground galaxy, NGC 7320, at 800 km/s, the extended continuum ridge near the center of the group, and 3 faint dwarf-like galaxies in the surrounding field were imaged with C, CS, and D arrays. Four of the HI clouds previously detected are confirmed. The two largest HI 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 coincide with tidal features south of NGC 7318a and the other devoid of any detectable stellar or Halfa sources. The two compact clouds, along the same line of sight, have peak emission at luminous infrared and bright Halfa sources probably indicative of star-forming activity. The total amount of HI detected at high redshifts is ~ 10**10Msol. As in previous HI studies of the group, no detectable emission was measured at the positions of any high-redshift galaxies so that any HI still bound to their disks must be less than 2.4 x 10**7Msol.