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L. Levy, J. A. Rose (U. of North Carolina - Chapel Hill), J. H. van Gorkom (Columbia University)
We present HI observations of 28 galaxies which complete the sample of spiral galaxies within 1 RA of the core Pegasus I cluster. The observations include single dish neutral Hydrogen measurements, obtained with the Arecibo telescope for all 28 galaxies in the sample, as well as HI spatial distribution maps, obtained with the VLA. The HI morphology of some galaxies shows that the HI is smaller than the optical disk and slightly offset from the stars. This could indicate an ICM-ISM interaction. This would be very surprising since the Pegasus cluster has a virtually undetectable level of X-ray emission, and a very low velocity dispersion. The low velocity dispersion, coupled with the lack of a dense hot ICM indicate that ram pressure stripping should not play a significant role in this environment. Nonetheless, we find evidence of some galaxies with HI deficiencies of up to a factor of 2 and with displaced HI. Also, two of the galaxies, NGC7604 and NGC7648, are morphologically peculiar. Their peculiarities indicate contradictory scenarios of what is triggering their unusual star formation. H\alpha imaging, along with long-slit spectroscopy of NGC7648 reveal morphological features which point to a recent tidal interaction. On the other hand, H\alpha imaging of NGC7604 reveals a strong episode of star formation concentrated into an symmetric arc, preferentially located on one side of the galaxy. VLA HI mapping shows the HI also highly concentrated into that region, suggestive of a ram pressure event. Our data hint at the possibility that ram pressure stripping may play a role in a wider variety of environments than previously considered.
The author(s) of this abstract have provided an email address for comments about the abstract: llevy@physics.unc.edu
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.