Neutral hydrogen mapping of Virgo Cluster blue compact dwarf galaxies
Hoffman, G. Lyle; Brosch, N.; Salpeter, E. E.; Carle, N. J.
A new installment of neutral hydrogen mappings of blue compact dwarf (BCD) galaxies, as defined by optical morphology, in and near the Virgo Cluster is presented. The primary motivation was to search for outlying clouds of H I as potential interactive triggers of enhanced star formation, and therefore the mapped galaxies were selected for large H I mass, large optical diameter, and large velocity profile width. Approximately half the sample proved to have one or more small, low column density, star-free companion clouds, either detached or appearing as an appendage in our maps, at a resolution on the order of 4 kpc. Comparison is made with a sample of similarly mapped field BCD galaxies drawn from the literature; however, the Virgo Cluster sample of mapped BCDs is still too small for conclusive comparisons to be made. We found, on the one hand, little or no evidence for ram-pressure stripping nor, on the other, for extremely extended low column density H I envelopes. The H I rotation curves in most cases rise approximately linearly and slowly, as far out as we can trace the gas.
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