Star-forming properties and histories of dwarf irregular galaxies: down but not out

• Published in: The Astrophysical journal. Supplement series Vol. 58; no. 4; pp. 533 - 560
• Main Authors: HUNTER, D. A, GALLAGHER, J. S. III
• Format: Journal Article
• Language: English
• Published: Chicago, IL University of Chicago Press 01.08.1985
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Interstellar medium (ism) and nebulae in external galaxies; Stellar systems. Galactic and extragalactic objects and systems. The universe; Stellar formation; Dwarf galaxies; Irregular galaxies; Stellar formation region; Data table; Structure; Spectroscopical observation
• ISSN: 0067-0049; 1538-4365
• DOI: 10.1086/191051

Spectroscopic and imaging data designed to study star formation processes in a sample of dwarf irregular (Irr) galaxies are presented. Although the low-surface brightness dwarf Irr's have much H I gas with which to form stars, the galaxy-wide star formation rates are low: typically about 10 to the -10th solar mass/yr/sq pc. The properties of the low-surface brightness dwarf Irr's are consistent with a constant star formation rate equal to their current rate over approximately a Hubble time. The typical star-forming regions in the dwarfs are on average smaller and less luminous than those in the giant Irr's, although the size distributions cover the same range, while similar to giant Irr's in many global parameters, the dwarfs have lower current and historical star formation rates per unit area. Dwarf Irr's have low metallicities relative to spirals, with typical nebular oxygen abundances falling between those of the LMC and SMC.