to IAU
Symposium 241

Abstract details

alpha-element enhancement effects on the Lick spectral indices and broad-band and SBF colors and magnitudes
Hyun-chul Lee

First, we present alpha-enhanced Lick spectral indices models at fixed [Fe/H] (rather than fixed heavy element mass fraction Z). Comparison of our models with observations of Milky Way and M31 globular clusters in index-index space are favorable, tracing the observations at a model age of 12 Gyr without any zero-point shifts that are needed by some other models. We also verify Beasley et al.'s recent hypothesis of the existence of young and intermediate-age star clusters in M31. Furthermore, we confirm the well-known enhancement of Mg and Na relative to Fe and Ca among early-type galaxies, and its increase with increasing velocity dispersion. There are distinct differences between globular clusters and galaxies in diagrams involving CN1 and CN2, hinting that the globular cluster environment may be a special one in terms of the amount of N incorporated into stars. Second, our preliminary version of SBF models indicate that alpha-enhanced models are needed to match massive red galaxies while solar-scaled models are fine for dwarf blue galaxies to reproduce their independently estimated ages and metallicities. Models are available at the

© 2006 IAC - XHTML CSS About