AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 19. Galaxy Clusters and Large Scale Structure
Oral, Monday, May 31, 1999, 10:00-11:30am, International Ballroom North

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[19.05] Neutral hydrogen in Stephan's Quintet

B. A. Williams (Univ. of Delaware), M. Yun (NRAO), L. Verdes-Montenegro (Instituto de Astrofisica de Andalucia)

Using the VLA, we have made new spectral-line observations of the neutral hydrogen in the direction of the compact group Stephan's Quintet. The high-velocity cloud components between 5600 and 6800 km/s and the disk of the foreground galaxy, NGC 7320, at 800 km/s, were successfully imaged with the C- and/or D-arrays. Given the high sensitivity and angular resolution of the data, we have generated maps of the distribution and velocity field of five spatially distinct HI substructures within the compact group. The observed line widths of these components are all very small, less than 180 km/s. Interestingly, the angular extent of the substructures correlates inversely with their observed line widths, i.e., the compact components have broader line widths while the more extended features have the narrower line profiles. No emission brighter than 0.4 mJy/beam was detected at the positions of any high-redshift galaxies in the quintet including NGC 7320C. Preliminary analysis of the velocity fields suggests that the HI gas between 5600 and 6100 km/s does not behave as a single dynamical feature or HI disk gravitationally bound to NGC 7318B or to any other member of the quintet.

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