Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt........26s&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF FLORIDA, 1995.Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6175
Other
5
Starbursts
Scientific paper
Dwarf irregular galaxies, which are small, low mass, asymmetrically shaped systems, are of interest both because of their large numbers and their usefulness as laboratories in which to study large-scale star formation. It is believed that these galaxies form stars through a process known as Stochastic Self-Propagating Star Formation (SSPSF) in which star formation occurs in episodic bursts involving most or all of the galaxy, with the time between starbursts increasing for smaller galaxies. The long quiescent intervals between star-forming episodes ensures that such galaxies spend much of their lives in an optically faint state. In this work, the results of (1) a survey to detect low mass dwarf irregular galaxies, and (2) a study of the atomic hydrogen in eight blue compact dwarfs and eight low surface brightness dwarfs are presented. To investigate a luminosity function, predicated upon SSPSF, that was postulated to rise steeply at the faint end, we conducted a survey, using the Very Large Array Radio Telescope, that was sensitive to low levels of atomic hydrogen (HI) emission. The survey, which was sensitive to HI masses as low as 2times10 ^5 M_odot, detected only four systems: the three catalogued target galaxies and another previously catalogued galaxy. This is in sharp contrast to the large number of systems predicted by the steeply rising luminosity function, and rules out the existence of a large number of low mass galaxies. The second part of this work examined the HI distributions and kinematics of a sample of 16 dwarf galaxies in varying stages of star-formation. This project investigated the effects of star-formation on the properties of low mass systems. The results of this study indicate that the state of the HI reservoirs in small galaxies is related to the evolutionary stage of the systems with respect to their star-formation histories. Less active galaxies are found to have more diffuse HI distributions, and the ring-like structure associated with some of the systems indicates that the HI has been disrupted. This is in accordance with the SSPSF scenario that predicts an expansion and contraction of the HI in response to the energy produced from a star-formation episode.
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