Stellar populations of early-type galaxies in different environments - II. Ages and metallicities



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Sánchez Blázquez, P. and Gorgas García, Francisco Javier and Cardiel López, Nicolás and González, J. J. (2006) Stellar populations of early-type galaxies in different environments - II. Ages and metallicities. Astronomy & Astrophysics, 457 (3). p. 809. ISSN 0004-6361

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This is the second paper of a series devoted to the study of the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects Methods. We use a new set of models that include an improved stellar library (MILES) to derive simple stellar population (SSP)-equivalent parameters in a sample of 98 early-type galaxies. The sample contains galaxies in the field, poor groups, and galaxies in the Virgo and Coma clusters. Results. We find that low-density environment galaxies span a larger range in SSP age and metallicity than their counterparts in high density environments, with a tendency for lower sigma galaxies to be younger. Early-type galaxies in low-density environments appear on average similar to 1.5 Gyr younger and more metal rich than their counterparts in high density environments. The sample of low-density environment galaxies shows an age-metallicity relation in which younger galaxies are found to be more metal rich, but only when metallicity is measured with a Fe-sensitive index. Conversely, there is no age-metallicity relation when the metallicity is measured with a Mg sensitive index. The mass-metallicity relation is only appreciable for the low-density environment galaxies when the metallicity is measured with a Mg-sensitive index, and not when the metallicity is measured with other indicators. On the contrary, this relation exists for the high-density environment galaxies independent of the indicator used to measure the metallicity. Conclusions. This suggests a dependence of the mass-metallicity relation on the environment of the galaxies. Our data favour a scenario in which galaxies in low density environments have suffered a more extended star formation history than the galaxies in the Coma cluster, which appear to host more homogenous stellar populations.

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© ESO 2006. We are very grateful to the referee, Jim Rose, for his very constructive report and many useful suggestions. We are also grateful to Javier Cenarro, Brad Gibson, Reynier Peletier, Daisuke Kawata, and Alexandre Vazdekis for many fruitful discussions. The Calar Alto Observatory is operated jointly by the Max-Planck Insitute für Astronomie, Heidelberg, and the Spanish Instituto de Astrofísica de Andalucía (CSIC). This work was supported by the Spanish research project AYA 2003-01840 and by the Australian Research Council. We are grateful to the CAT for generous allocation of telescope time.

Uncontrolled Keywords:Dynamically hot galaxies; Dwarf elliptic galaxies; Central black-holes; Dark-matter haloes; Coma cluster; S0 galaxies; Spectral-resolution; Chemical enrichment; Evolutionary tracks; Globular-clusters
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
ID Code:28320
Deposited On:11 Feb 2015 16:06
Last Modified:10 Dec 2018 15:05

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