The abundance spread in the Bootes I dwarf spheroidal galaxy

TL;DR

This study analyzes the chemical abundance spread in the Bootes I dwarf spheroidal galaxy using medium-resolution spectra of red giants, revealing a significant metallicity variation similar to larger systems, implying dark matter's role in its evolution.

Contribution

First measurement of metallicity distribution in Bootes I dSph using Ca II K line spectra, highlighting its large abundance spread and implications for dark matter influence.

Findings

Abundance range Delta [Fe/H] ~ 1.7 dex among members.

Metallicity dispersion sigma([Fe/H]) = 0.45 +/- 0.08.

Similar chemical spread to larger dwarf galaxies and Omega Centauri.

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 Delta [Fe/H] ~ 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 approximately 10 million solar masses) normally assumed to foster self-enrichment and the production of chemical abundance spreads was provided by the non-baryonic material in Bootes I.