THE ABUNDANCE SPREAD IN THE BOOTES I DWARF SPHEROIDAL GALAXY

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] similar to 0.3, the abundance range in the sample is Delta[Fe/H] similar to 1.7 dex, with one star having [Fe/H] = -3.4. The dispersion is sigma([Fe/H]) = 0.45 +/- 0.08-similar to those of the Galaxy's more luminous dSph systems and omega Centauri. This suggests that the large mass (greater than or similar to 10(7) M-circle dot) normally assumed to foster self-enrichment and the production of chemical abundance spreads was provided by the nonbaryonic material in Bootes I.