Abstract
Some of the lowest-mass dwarf irregular galaxies, such as Leo A, Sag DIG and Cas 1, show a characteristic distribution of their neutral interstellar medium (ISM) as observed in the 21cm line of neutral hydrogen (HI): the majority of the gas is found to be concentrated in a ring-like feature centred on, and embracing the optical counterparts of these objects. We present multi-array, high-resolution VLA HI and deep optical observations of Holmberg I and M81 dw A, both members of the M81 group of galaxies. Their HI is mainly stored at a galactocentric radius of about 0.8 kpc, at the edge of the optical images. The rings show neither expansion nor contraction.
| Original language | English |
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| Title of host publication | In: Procs of Mapping the Hidden Universe: The Universe behind the Milky Way - The Universe in HI, ASP Conf Series 218 |
| Publisher | Astronomical Society of the Pacific |
| Pages | 373-378 |
| ISBN (Print) | 1-58381-050-1 |
| Publication status | Published - 2000 |