Neutral Hydrogen Observations
of Blue Compact Dwarf Galaxies

While the most luminous starbursts are found in interacting and merging systems, the lowest luminosity starburst galaxies - blue compact dwarfs (BCD) - tend to be isolated. We imaged the neutral hydrogen content of two BCDs, NGC2915, and NGC1705, using the Australia Telescope Compact Array in order to determine the global dynamics of the host and to look for signs of an external trigger to the starburst. Both show HI disks extending well beyond their optical extent and flat rotation curves at large radius. They are dark matter dominated at nearly all radii, and their dark matter cores have unusually high densities compared to dwarf irregular and spiral galaxies. Complimentary optical images were obtained primarily with the Anglo-Australian Telescope.

NGC2915 is a relatively quiescent BCD at a distance of 5 Mpc. It has some star clusters in its center and the typical H-alpha bubbles of a windy galaxy. None of these are that spectacular compared to those in other BCDS. Instead, its most remarkable feature is its extended HI disk, complete with HI spiral arms, but with no detectable underlying stellar emission. This picture mixes two images: HI in blue and broad (I) band optical in yellow.   Optical Study: Meurer et al (1994) HI study: Meurer et al (1996)

NGC1705 at a distance of about 6 Mpc is a very active BCD as made evident by its very blue color, and a strong galactic wind seen in H-alpha. It hosts a young (about 10 Myr) super star cluster with a mass of around 106 Msun, which may be the main source of mechanical energy for the outflow. This picture mixes three images: neutral Hydrogen (HI) in (cyan) blue, broad (B) band optical in green, and ionized hydrogen in red.   Optical study: Meurer et al. (1992).    (Optical write-up) Ultraviolet study: Meurer et al. (1995).    (UV image gallery) HI study: Meurer, Stavely-Smith, & Killeen (1998)

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