Program: GS-2007B-Q-53

Title:The ABCs of BCDs
PI:Eduardo Unda-Sanzana
Co-I(s): Ovidiu Vaduvescu, Marshall McCall, Henry Lee

Abstract

Recent studies of the near-infrared (NIR) properties of dwarf irregular galaxies (dIs) and blue compact dwarfs (BCDs) have provided improved estimates for the NIR luminosity of old stellar populations in these galaxies (Vaduvescu et al. 2005, Vaduvescu, Richer, & McCall 2006). Knowledge of the evolutionary status of BCDs is pivotal to understanding the origin of other kinds of dwarfs, most especially dwarf spheroidals (dSphs), and the nature of faint blue galaxies at z~1. Recent chemical studies of dwarfs have shown that field dIs and Virgo BCDs appear to share a common relation between the oxygen abundance and the luminosity in K (Vaduvescu, McCall, & Richer 2007). Moreover, the correlation between metallicity and the gas fraction appears to be the same for BCDs as for dIs, suggesting that BCD evolution is similar to that of dIs. Based on these results, it has become possible to trace the evolution of BCDs with respect to dIs, and in so doing to pinpoint the physical parameters controlling dwarf evolution. In the present application the authors propose to scrutinize the evolution of BCDs with respect of dIs even further. We propose to use GMOS on Gemini South to measure oxygen abundances in 10 BCDs in Fornax cluster. This proposal has two main science objectives: to evaluate the chemical evolution of "clean" BCDs with respect to dIs, and to evaluate the effect of the environment on the evolution of BCDs. An additional result of this study will be the comparison of the chemical evolution of BCDs in the Virgo and Fornax clusters. Masses and gas fractions for cluster BCDs and a control sample of field dIs are being quantified through NIR imaging.

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