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

By P. Sánchez-Blázquez, J. Gorgas, N. Cardiel, J. González. 2006

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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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b5875dfe0d9a0f784d55b85e7246b358ffb753e2

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Citations in the corpus

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models (2015, methodology): “In fact, it is possible to obtain a good proxy for the [Mg/Fe] abundance, if appropriate indices are employed for the analysis (Vazdekis et al. 2001b, 2010; Sánchez-Blázquez et al. 2006c; Yamada et al. 2006; de la Rosa et al. 2007; Michielsen et al. 2008; La Barbera et al. 2013).”
Evolutionary stellar population synthesis with MILES – I. The base models and a new line index system (2010, methodology): “0Å, or to correct his/her measurements to a total broadening of 8.4 Å(FWHM) using polynomials (see, e.g., Kuntschner 2000; Sánchez-Blázquez et al. 2006a).”
Spatially resolved spectroscopy of early-type galaxies over a range in mass (2007, methodology): “For the stellar templates, we use synthetic stellar energy distributions from Vazdekis et al. (2007) based on the MILES stellar library (Sánchez-Blázquez et al. 2006d).”
UV-extended E-MILES stellar population models: young components in massive early-type galaxies (2016, methodology): “These SSP spectra were joined to those computed with MILES (Sánchez-Blázquez et al. 2006) in the optical range, as well as with our models for redder wavelengths, all computed with the same code and prescriptions and employing empirical stellar libraries, i.e. IndoUS (Valdes et al. 2004), CAT…”