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arXiv · 0909.5385

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

E. Mármol-Queraltó·N. Cardiel·P. Sánchez-Blázquez·S. C. Trager·R. F. Peletier·H. Kuntschner·D. R. Silva·A. J. Cenarro·A. Vazdekis·J. Gorgas
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Abstract

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 RGB dominate the integrated light at all ages. The near-infrared spectral range is especially interesting since in the presence of an intermediate-age population, AGB stars are the main contributors. In this letter, we measure the near-infrared indices NaI and D$_{\rm CO}$ 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. (2008). The analysis of these indices in combination with Lick/IDS indices in the optical range reveals i) the NaI index is a metallicity indicator as good as C4668 in the optical range, and ii) D$_{\rm CO}$ is a tracer of intermediate-age stellar populations. We find that low-mass galaxies in low density environments show higher NaI and D$_{\rm CO}$ than those located in Fornax cluster, which points towards 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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E. Mármol-Queraltó, N. Cardiel, P. Sánchez-Blázquez, S. C. Trager, R. F. Peletier, H. Kuntschner, D. R. Silva, A. J. Cenarro, A. Vazdekis, J. Gorgas. 2009-09-29. Evidence for intermediate-age stellar populations in early-type galaxies from K-band spectroscopy. https://doi.org/10.1088/0004-637x%2F705%2F2%2Fl199

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