5 research outputs found
Chemical Abundances of the Leo II Dwarf Galaxy
We use previously-published moderate-resolution spectra in combination with
stellar atmosphere models to derive the first measured chemical abundance
ratios in the Leo II dSph galaxy. We find that for spectra with SNR > 24, we
are able to measure abundances from weak Ti, Fe and Mg lines located near the
calcium infrared triplet (CaT). We also quantify and discuss discrepancies
between the metallicities measured from Fe I lines and those estimated from the
CaT features. We find that while the most metal-poor ([Fe/H] <-2.0]) Leo II
stars have Ca and Ti abundance ratios similar to those of Galactic globular
clusters, the more metal-rich stars show a gradual decline of Ti, Mg and Ca
abundance ratio with increasing metallicity. Finding these trends in this
distant and apparently dynamically stable dSph galaxy supports the hypothesis
that the slow chemical enrichment histories of the dSph galaxies is universal,
independent of any interaction with the Milky Way. Combining our spectroscopic
abundances with published broadband photometry and updated isochrones, we are
able to approximate stellar ages for our bright RGB stars to a relative
precision of 2-3 Gyr. While the derived age-metallicity relationship of Leo II
hints at some amount of slow enrichment, the data are still statistically
consistent with no enrichment over the history of Leo II.Comment: Accepted to A