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

## [11.07] HI--line Observations of Low Surface Brightness Dwarf Galaxies

D. L. Thomas (NRAO--Socorro), C. L. Taylor (McMaster U.), E. Brinks (NRAO--Socorro), E. D. Skillman (U. Minnesota)

We present HI--line observations of low--surface brightness (LSB) dwarf galaxies to survey their nearby environment (r \leq 100 kpc) for HI bright companions. It is possible that star formation histories in dwarf galaxies can be strongly affected by interactions with nearby companions. If massive star formation can be triggered by galaxy--galaxy interactions, then the absence of such interactions likely explains the lack of star formation in LSB dwarf galaxies relative to their high surface brightness counterparts (HII galaxies). Taylor et al.\ (1995, ApJS, 99, 427) surveyed a sample of HII galaxies and found that 60% of the sample had nearby HI companions. In our sample of 18 LSB galaxies, we found that only 22% had companions detectable in HI. Furthermore, we find that the peak column densities for the LSB sample are all below 10^21 HI atoms cm^-2. This is below the empirically established level needed for star formation to occur in dwarf galaxies as discussed by Skillman (1987, in Star Formation in Galaxies, ed. C.J. Lonsdale Persson (NASA Conf. Pub. CP--2466), p.263), Kennicutt (1989, ApJ, 344, 685), van der Hulst et al.\ (1993, AJ, 106, 548), and Taylor et al.\ (1994, AJ, 107, 971).