The Abundance Spread in the Bootes I Dwarf Spheroidal Galaxy

Abstract

We present medium-resolution spectra of 16 radial velocity red-giant members of the low-luminosity Bootes I dwarf spheroidal (dSph) galaxy that have sufficient S/N for abundance determination, based on the strength of the Ca ii K line. Assuming [Ca/Fe]-0.3, the abundance range in the sample is Δ[Fe/H]-1.7 dex, with one star having [Fe/H]=-3.4. The dispersion is σ([Fe/H])=0.45 ± 0.08-similar to those of the Galaxy's more luminous dSph systems and ω Centauri. This suggests that the large mass (⊙≥10 7 M&o) normally assumed to foster self-enrichment and the production of chemical abundance spreads was provided by the nonbaryonic material in Boötes I.