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The impact of alpha/Fe enhanced stellar evolutionary tracks on the ages of elliptical galaxies

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The impact of alpha/Fe enhanced stellar evolutionary tracks on the ages of elliptical galaxies. / Thomas, D.; Maraston, C.

In: Astronomy and Astrophysics, Vol. 401, No. 2, 02.04.2003, p. 429-432.

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@article{95cbdce99df44708808f7a7f99a659bd,
title = "The impact of alpha/Fe enhanced stellar evolutionary tracks on the ages of elliptical galaxies",
abstract = "We complement our study of α/Fe enhanced stellar population models of Lick absorption indices (Thomas et al. 2003) by comparing two sets of α/Fe enhanced models. In both models the impact on Lick indices due to α/Fe enhancement is accounted for through a modification of the stellar absorption line-strengths using the response functions of Tripicco & Bell (1995). One set of models, however, uses solar-scaled, the other α/Fe enhanced stellar evolutionary tracks. Since the α/Fe enhanced tracks are hotter than the solar-scaled ones (Salasnich et al. 2000), the correspondent stellar population models have slightly weaker metallic indices (i.e. Mgb, <Fe> etc.) and stronger Balmer line indices (Hβ) (Maraston et al. 2003). Here we explore quantitatively the impact of this effect on the α/Fe ratios, metallicities and ages that are derived for elliptical galaxies. We find that the modest decrease of the metallic indices Mg b and <Fe> balance each other, such that fully consistent α/Fe ratios are derived for stellar systems using α/Fe enhanced models with either solar-scaled or α/Fe enhanced stellar tracks. The decrease of the metallic indices and the increase of H conspire in a way that also consistent metallicities are obtained. The derived ages, instead, are significantly different. The inclusion of α/Fe 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 α/Fe 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 α/Fe enhanced chemical mixtures at super-solar metallicities.",
keywords = "stars : evolution, stars : abundances, galaxies : stellar content, galaxies : elliptical and lenticular, cD, galaxies : formation",
author = "D. Thomas and C. Maraston",
note = "copyright ESO 2003",
year = "2003",
month = apr,
day = "2",
doi = "10.1051/0004-6361:20030153",
language = "English",
volume = "401",
pages = "429--432",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "2",

}

RIS

TY - JOUR

T1 - The impact of alpha/Fe enhanced stellar evolutionary tracks on the ages of elliptical galaxies

AU - Thomas, D.

AU - Maraston, C.

N1 - copyright ESO 2003

PY - 2003/4/2

Y1 - 2003/4/2

N2 - We complement our study of α/Fe enhanced stellar population models of Lick absorption indices (Thomas et al. 2003) by comparing two sets of α/Fe enhanced models. In both models the impact on Lick indices due to α/Fe enhancement is accounted for through a modification of the stellar absorption line-strengths using the response functions of Tripicco & Bell (1995). One set of models, however, uses solar-scaled, the other α/Fe enhanced stellar evolutionary tracks. Since the α/Fe enhanced tracks are hotter than the solar-scaled ones (Salasnich et al. 2000), the correspondent stellar population models have slightly weaker metallic indices (i.e. Mgb, <Fe> etc.) and stronger Balmer line indices (Hβ) (Maraston et al. 2003). Here we explore quantitatively the impact of this effect on the α/Fe ratios, metallicities and ages that are derived for elliptical galaxies. We find that the modest decrease of the metallic indices Mg b and <Fe> balance each other, such that fully consistent α/Fe ratios are derived for stellar systems using α/Fe enhanced models with either solar-scaled or α/Fe enhanced stellar tracks. The decrease of the metallic indices and the increase of H conspire in a way that also consistent metallicities are obtained. The derived ages, instead, are significantly different. The inclusion of α/Fe 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 α/Fe 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 α/Fe enhanced chemical mixtures at super-solar metallicities.

AB - We complement our study of α/Fe enhanced stellar population models of Lick absorption indices (Thomas et al. 2003) by comparing two sets of α/Fe enhanced models. In both models the impact on Lick indices due to α/Fe enhancement is accounted for through a modification of the stellar absorption line-strengths using the response functions of Tripicco & Bell (1995). One set of models, however, uses solar-scaled, the other α/Fe enhanced stellar evolutionary tracks. Since the α/Fe enhanced tracks are hotter than the solar-scaled ones (Salasnich et al. 2000), the correspondent stellar population models have slightly weaker metallic indices (i.e. Mgb, <Fe> etc.) and stronger Balmer line indices (Hβ) (Maraston et al. 2003). Here we explore quantitatively the impact of this effect on the α/Fe ratios, metallicities and ages that are derived for elliptical galaxies. We find that the modest decrease of the metallic indices Mg b and <Fe> balance each other, such that fully consistent α/Fe ratios are derived for stellar systems using α/Fe enhanced models with either solar-scaled or α/Fe enhanced stellar tracks. The decrease of the metallic indices and the increase of H conspire in a way that also consistent metallicities are obtained. The derived ages, instead, are significantly different. The inclusion of α/Fe 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 α/Fe 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 α/Fe enhanced chemical mixtures at super-solar metallicities.

KW - stars : evolution

KW - stars : abundances

KW - galaxies : stellar content

KW - galaxies : elliptical and lenticular, cD

KW - galaxies : formation

U2 - 10.1051/0004-6361:20030153

DO - 10.1051/0004-6361:20030153

M3 - Article

VL - 401

SP - 429

EP - 432

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 2

ER -

ID: 1795610