Evidence for intermediate-age stellar populations in early-type galaxies from K-band spectroscopy



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Mármol Queraltó, E. and Cardiel López, Nicolás and Sánchez Blázquez, P. and Trager, S. C. and Peletier, R. F. and Kuntschner, H. and Silva, D. R. and Cenarro, A. J. and Vazdekis, A. and Gorgas García, Francisco Javier (2009) Evidence for intermediate-age stellar populations in early-type galaxies from K-band spectroscopy. Astrophysical Journal Letters, 705 (2). ISSN 2041-8205

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Official URL: http://dx.doi.org/10.1088/0004-637X/705/2/L199


The study of stellar populations in early-type galaxies in different environments is a powerful tool for constraining their star formation histories. This study has been traditionally restricted to the optical range, where dwarfs around the turn-off and stars at the base of the red giant branch dominate the integrated light at all ages. The near-infrared spectral range is especially interesting since in the presence of an intermediate-age population, asymptotic giant branch stars are the main contributors. In this Letter, we measure the near-infrared indices Na I and D(CO) for a sample of 12 early-type galaxies in low-density environments and compare them with the Fornax galaxy sample presented by Silva et al.. The analysis of these indices in combination with Lick/IDS indices in the optical range reveals that (1) the Na I index is a metallicity indicator as good as C4668 in the optical range, and (2) D(CO) is a tracer of intermediate-age stellar populations. We find that low-mass galaxies in low-density environments show higher Na I and D(CO) than those located in the Fornax cluster, which points toward a late stage of star formation for the galaxies in less dense environments, in agreement with results from other studies using independent methods.

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© 2009. The American Astronomical Society. The authors acknowledge the referee, Bahram Mobasher, for his useful comments. E. M.-Q. acknowledges the SMES for a FPI PhD fellowship. This work has been partially supported by the SMES through the research project AYA2007-67752-C0301. N. C. also acknowledges financial support from the research project AYA2006-15698-C02-02. P. S.-B. acknowledges the financial support from a Marie Curie European Reintegration Grant within the 7th European Community Framework Programme.

Uncontrolled Keywords:Low-density environments; Elliptic galaxies; Nitrogen abundances; Globular-clusters; Fornax cluster; Lick indexes; S0 galaxies; Mu-M; Metallicity; Calibration
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
ID Code:28023
Deposited On:26 Jan 2015 08:29
Last Modified:10 Dec 2018 15:05

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