Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models

A. Vazdekis; P. Coelho; S. Cassisi; E. Ricciardelli; J. Falcón-Barroso; P. Sánchez-Blázquez; F. La Barbera; M. A. Beasley; A. Pietrinferni

doi:10.1093/mnras/stv151

paper

Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models

arXiv:1504.08032 · doi:10.1093/mnras/stv151

Abstract

We present models that predict spectra of old- and intermediate-aged stellar populations at 2.51Å (FWHM) with varying [α/Fe] abundance. The models are based on the MILES library and on corrections from theoretical stellar spectra. The models employ recent [Mg/Fe] determinations for the MILES stars and BaSTI scaled-solar and α-enhanced isochrones. We compute models for a suite of IMF shapes and slopes, covering a wide age/metallicity range. Using BaSTI, we also compute "base models" matching The Galactic abundance pattern. We confirm that the α-enhanced models show a flux excess with respect to the scaled-solar models blue-ward $\sim$ 4500Å, which increases with age and metallicity. We also confirm that both [MgFe] and [MgFe]' indices are [α/Fe]-insensitive. We show that the sensitivity of the higher order Balmer lines to [α/Fe] resides in their pseudo-continua, with narrower index definitions yielding lower sensitivity. We confirm that the α-enhanced models yield bluer (redder) colours in the blue (red) spectral range. To match optical colours of massive galaxies we require both α-enhancement and a bottom-heavy IMF. The comparison of Globular Cluster line-strengths with our predictions match the [Mg/Fe] determinations from their individual stars. We obtain good fits to both full spectra and indices of galaxies with varying [α/Fe]. Using thousands of SDSS galaxy spectra we obtain a linear relation between a proxy for the abundance, [Z $_{Mg}$ /Z $_{Fe}$ ] $_{SS (BaSTI)}$ , using solely scaled-solar models and the [Mg/Fe] derived with models with varying abundance ([Mg/Fe]=0.59[Z $_{Mg}$ /Z $_{Fe}$ ] $_{SS (BaSTI)}$ ). Finally we provide a user-friendly, web-based facility, which allows composite populations with varying IMF and [α/Fe] ( http://miles.iac.es ).

arXiv commentPublished in MNRAS,449,1177 (2015) http://adsabs.harvard.edu/abs/2015MNRAS.449.1177V . Models can be downloaded from http://miles.iac.es

Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models

Abstract

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