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|Title:||Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models||Authors:||Vazdekis, A.
LA BARBERA, Francesco
Beasley, M. A.
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||449||Issue:||2||First Page:||1177||Abstract:||We present models that predict spectra of old- and intermediate-aged stellar populations at 2.51 Å (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 initial mass function (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 blueward ̃4500 Å, 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<SUB>Mg</SUB>/Z<SUB>Fe</SUB>]<SUB>SS(BaSTI)</SUB>, using solely scaled-solar models and the [Mg/Fe] derived with models with varying abundance ([Mg/Fe] = 0.59[Z<SUB>Mg</SUB>/Z<SUB>Fe</SUB>]<SUB>SS(BaSTI)</SUB>). Finally, we provide a user-friendly, web-based facility, which allows composite populations with varying IMF and [α/Fe].||Acknowledgments:||We are indebted to the Padova group for making their isochrone calculations available to us. We are grateful to A. de C. Milone for providing us with his [Mg/Fe] estimates for the stars of the MILES library before publication. We also are grateful to H.-S. Kim, J. Cho, R. M. Sharples and S.-J. Yoon, who provided us with GGC line-strength measurements prior to publication. We are grateful to B. Barbuy, J. L. Cervantes, I. G. de la Rosa, M. Koleva, R. Peletier and A. Sansom for very useful discussions. We thank the referee H.-C. Lee for a careful reading of the manuscript and for very valuable clarifications that helped us to improve the manuscript. We also would like to thank J. A. Perez Prieto for helping us in the construction of the web page for the models. The MILES library was observed at the INT on the island of La Palma, operated by the Isaac Newton Group at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. This research has made an extensive use of the SIMBAD data base and VizieR catalogue access tool (both operated at CDS, Strasbourg, France), the NASA's Astrophysics Data System Article Service. We made use of data retrieved from the Sloan Digital Sky Survey archives ( http://www.sdss.org ). Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. PC acknowledges the financial support by FAPESP via project 2008/58406-4 and fellowship 2009/09465-0. JFB acknowledges support from the Ramón y Cajal programme by the Spanish Ministry of Economy and Competitiveness (MINECO). This work has been supported by the Programa Nacional de Astronomía y Astrofísica of MINECO, under grants AYA2013-48226-C3-1-P, AYA2013-48226-C3-2-P, AYA2013-48226-C3-3-P and by the Generalitat Valenciana under grant PROMETEOII2014-069.||URI:||http://hdl.handle.net/20.500.12386/23798||URL:||https://academic.oup.com/mnras/article/449/2/1177/1063256||ISSN:||0035-8711||DOI:||10.1093/mnras/stv151||Bibcode ADS:||2015MNRAS.449.1177V||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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