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M. W. Buckley (MIT), K. Flint (Carnegie Institution of Washington-DTM), C. D. Impey (Steward Observatory), M. Bolte (UCO/Lick Observatory)
Using a wide-field radio survey we determined the HI mass distribution in Leo I, a low-density group of galaxies located at a distance of 10 Mpc. HI spectral line data were collected using the L-narrow receiver of the Arecibo Radio telescope. The telescope was operated in scanning mode in order to completely map a 3 \arcdeg \times 3 \arcdeg section of sky, matching that covered by a deep optical survey by Flint et al. (2001, ApJS, 134, 53). The survey is sensitive over the velocity range 0 < v < 5000 km/s to a low-mass limit of 1.1 \times 107 M\sun at a distance of 10 Mpc. The advantage of conducting this type of blind survey is that it will detect all the galaxies present down to the HI mass limit rather than being biased toward optically bright galaxies.
Apart from the two large spiral galaxies, NGC3368 and NGC3351, most of the HI detections found by the survey were associated with a known HI ring in the group's core. None of the dwarf galaxies in Leo I had sufficient HI gas to be detected by our survey, which suggests that the HI mass function of Leo I may exhibit a lack of intermediate mass objects similar to the observed gap in the luminosity function between -19.5 < MR < -16 (Flint et al. 2003, Ap&SS, 285, 191). No galaxies were detected in HI which had not been previously detected optically, which suggests that there are no gas-rich dark-matter dominated galaxies present in Leo I down to our limits.
This work was supported by the Carnegie Institution of Washington and NSF REU Program Award #0097569.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.