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Session 11 - LMC, Dwarf Galaxies.
Display session, Monday, January 15
North Banquet Hall, Convention Center

[11.06] Ultraviolet Imaging Telescope Observations of Dwarf Galaxies

S. E. Gessner (Univ. of Alabama), J. K. Hill (Hughes-STX), K. Cheng (CSU), R. C. Bohlin (STScI), R. W. O'Connell (UVa), P. M. N. Hintzen (NASA/GSFC,CSU), M. S. Roberts (NRAO), S. G. Neff, A. M. Smith, E. P. Smith, T. P. Stecher (NASA/GSFC)

Dwarf galaxies provide a unique environment in which to study the causes and effects of star formation in a system. Compared to spiral galaxies, dwarf galaxies usually lack a spiral density wave and a high metallicity to trigger and regulate star formation. They also exhibit low rotational velocities and solid body rotation allowing features in their ISM to be longer lived. The spatial pattern of star formation and its relation to the galaxy's ISM can easily be traced through a comparison of the ionized and neutral gases. Thus far, investigations of these two components in dwarf galaxies have mainly been conducted with H\alpha and H \smallI\normalsize data. Here, we are given another look at the ionized medium in dwarf galaxies provided by the direct and dust scattered stellar continuum from ultraviolet images. We present new observations of three dwarf galaxies taken by the Ultraviolet Imaging Telescope (UIT) during the recent ASTRO-2 mission (STS-67). Far-ultraviolet observations at 1520 Å\ and 1615 Å\ of the dwarf irregular galaxies Holmberg 2 and Sextans A and the dwarf spiral galaxy IC 2574 are compared with groundbased optical and 21 cm observations. Specifically, positions of star clusters seen in the ultraviolet are correlated with H\alpha and H \smallI\normalsize data to reveal the impact of star formation on the ISM of these dwarf systems. Ages of previously identified H \smallII\normalsize regions are determined by measuring the ratio of H\alpha to far-ultraviolet flux and estimating the internal extinction in the galaxies. Ionized gas structures identified by Hunter, Hawley, and Gallagher (1993) as seen in the ultraviolet are discussed as is the possible presence of a far-ultraviolet diffuse emission component.

Support from the Alabama Space Grant Consortium Fellowship Program, the University of Alabama Graduate School, and the Mt. Laguna Observatory are recognized.

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