Program: GS-2008A-Q-49

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

Abstract

Recent studies of the near-infrared (NIR) properties of dwarf irregular galaxies (dIs) and blue compact dwarfs (BCDs) observed in the field and nearby clusters 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 higher redshifts. 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). 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. An incoming run on Gemini-South is expected to bring new data for about 6 BCDs in Fornax Cluster. Based on these results, we will be able to start tracing the evolution of BCDs with respect to dIs in different environments, and in so doing to pinpoint the physical parameters controlling dwarf evolution. In the present application we propose to scrutinize the evolution of BCDs with respect of dIs in a new environment. We propose to use GMOS on Gemini South in Band 3 conditions in order to measure accurate oxygen abundances in about 6-10 BCDs in Hydra cluster. This proposal has two main science objectives: to study the chemical evolution of 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 three cluster enviromnets: Virgo, Fornax and Hydra, which will make the object of a paper in progress. Masses and gas fractions for cluster BCDs are being quantified in parallel, via NIR imaging.

Publications using this program's data