Issue |
A&A
Volume 401, Number 2, April II 2003
|
|
---|---|---|
Page(s) | 429 - 432 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20030153 | |
Published online | 21 March 2003 |
The impact of α/Fe enhanced stellar evolutionary tracks on the ages of elliptical galaxies
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: dthomas@mpe.mpg.de;maraston@mpe.mpg.de
Corresponding author: D. Thomas, dthomas@mpe.mpg.de
Received:
16
September
2002
Accepted:
30
January
2003
We complement our study of enhanced stellar
population models of Lick absorption indices (Thomas et al. [CITE]) by
comparing two sets of
enhanced models. In both models the impact
on Lick indices due to
enhancement is accounted for through a
modification of the stellar absorption line-strengths using the
response functions of Tripicco & Bell ([CITE]). One set of models, however, uses
solar-scaled, the other
enhanced stellar evolutionary
tracks. Since the
enhanced tracks are hotter than the
solar-scaled ones (Salasnich et al. [CITE]), the correspondent stellar
population models have slightly weaker metallic indices (i.e.
,
etc.) and stronger Balmer line indices (
)
(Maraston et al. [CITE]). Here we explore quantitatively the impact of this
effect on the
ratios, metallicities and ages that are derived
for elliptical galaxies. We find that the modest decrease of the
metallic indices
and
balance each other, such that fully
consistent
ratios are derived for stellar systems using
enhanced models with either solar-scaled or
enhanced stellar
tracks. The decrease of the metallic indices and the increase of
conspire in a way that also consistent metallicities are obtained.
The derived ages, instead, are significantly different. The inclusion
of
enhanced stellar tracks leads to the derivation of ages as
high as ~30 Gyr for elliptical galaxies. For the same objects,
ages not older than 15 Gyr are obtained, if
enhanced models
using solar-scaled tracks are adopted. This may indicate that current
stellar evolutionary models overestimate the bluing of stellar
evolutionary tracks due to
enhanced chemical mixtures at
super-solar metallicities.
Key words: stars: evolution / stars: abundances / galaxies: stellar content / galaxies: elliptical and lenticular, cD / galaxies: formation
© ESO, 2003
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