Elemental Enrichment and Stellar Populations of Gas-Rich Low Surface Brightness Galaxies

van Zee, L., Haynes, M.P., & Salzer, J.J. 1997, AJ, 114, 2497

Abstract

The results of evolutionary studies of 15 gas-rich, low surface brightness dwarf galaxies (LSBDG's) are presented. The LSBDG's are distinguished by high values of hydrogen-mass-to-optical-luminosity and the presence of extended HI envelopes. While these properties suggest a relatively inefficient star formation history, these objects are not ``young'' systems. Based on UBVR colors, the dominant stellar populations are at least 2-4 Gyr old. The derived oxygen abundances are low and are in agreement with the previously known metallicity-luminosity relation for low mass objects. Similar to other studies of relative enrichments of heavy elements in low mass systems, the observed N/O ratio suggests a primary origin of nitrogen in low abundance systems. While outflow or inflow of gas cannot be ruled out (particularly in such gas-rich systems), closed box estimates with normal nucleosynthetic yields are consistent with the observed metallicities.