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abstract
S0 galaxies form an important transition between elliptical and spiral galaxies. It is therefore important to understand the extent of star formation in these systems and its relation to the gas content. We have studied one gas-rich S0 galaxy UGC 491. Optical CCD images were obtained in B, R, and continuum-subtracted H-alpha-N II. The neutral hydrogen content was mapped with the VLA in the C-array (a 15 aresec beam) with a velocity resolution of 21 km/s. IRAF was used to perform elliptical isophotal fitting and surface photometry. The total integrated magnitude for B is 13.7 mag, and for R it is 12.2 mag. A comparison of the radial profiles of (B-R) and H-alpha flux with the H I surface density and the predicted critical gas density (Kennicutt 1989) provides insight into the star formation properties of this gas-rich S0. We derive the star formation rate from the H-alpha flux and compare this with that for other types of spiral galaxies. We conclude that many gas-rich S0 galaxies could be classified as anemic spirals with low surface brightness spiral structure and/or isolated regions of star formation.
