We present medium-resolution spectra of 16 radial velocity red-giant members of the low-luminosity Boötes 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 ] \sim 0.3 , the abundance range in the sample is \Delta [ Fe/H ] \sim 1.7 dex , with one star having [ Fe/H = –3.4 .
The dispersion is \sigma ( [ Fe/H ] ) = 0.45 \pm 0.08 – similar to those of the Galaxy ’ s more luminous dSph systems and \omega Centauri .
This suggests that the large mass ( \gtrsim 10 ^ { 7 } ~ { } M _ { \odot } ) normally assumed to foster self-enrichment and the production of chemical abundance spreads was provided by the non-baryonic material in Boötes I .