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Atomic hydrogen, star formation and feedback in the lowest mass blue compact dwarf galaxies


E-mail: (SR); (JNC); (KC); (IDK); (RBT); (SSK)


We present the results from a search for H i emission from a sample of newly discovered dwarf galaxies in the M81 group. H i is detected in three galaxies, all of which are classified as blue compact dwarf galaxies (BCDs). The H i masses of these galaxies are ∼106 M, making them some of the lowest mass BCDs known. For these three galaxies far-ultraviolet (FUV) images (from GALEX) and Hα images (from the Russian 6 m BTA telescope) are available. The Hα emission is very faint and, in principle, could be produced by a single O star. Further, in all cases we find offsets between the peak of the FUV emission and that of the Hα emission. Offsets between the most recent sites of star formation (i.e. those traced by Hα) and the older sites (i.e. those traced by FUV) would be natural if the star formation is stochastic. In spite of the expectation that the effects of mechanical feedback from star formation would most directly be seen in the smallest galaxies with low gravitational potentials, we only see tentative evidence of outflowing H i gas associated with the star-forming region in one of the galaxies.