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The southern sample of extremely late-type galaxies within the Local Supercluster described by Matthews and Gallagher (this meeting) has been used to explore relationships between global kinematics, optical structures, environments, and evolutionary histories of small field galaxies. Pencil beam 21-cm HI measurements of these galaxies yield global HI line profiles that provide information on the forms and amplitudes of the rotation curves. These data in combination with results from our CTIO CCD optical imaging allow us to investigate how rotation curves and stellar content are related in extremely late-type galaxies. This important correlation gives rise to the Tully-Fisher relationship in more luminous spirals, which breaks down for less luminous galaxies. We also will look for systematic variations in HI profiles with optical structures (e.g., the more organized, dwarf spiral-like objects versus true irregulars, high versus low central V brightnesses, presence of bars); stellar population properties derived from B-V colors; and environments (dense versus sparse regions of galaxy groups). The outcome of this study will be discussed in terms of the origins and evolution of the most common classes of star-forming galaxies.
Tuesday program listing