2009ApJ...705L.199M -
Astrophys. J., 705, L199-L203 (2009/November-2)
Evidence for intermediate-age stellar populations in early-type galaxies from k-band spectroscopy.
MARMOL-QUERALTO E., CARDIEL N., SANCHEZ-BLAZQUEZ P., TRAGER S.C., PELETIER R.F., KUNTSCHNER H., SILVA D.R., CENARRO A.J., VAZDEKIS A. and GORGAS J.
Abstract (from CDS):
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 DCO 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) DCO is a tracer of intermediate-age stellar populations. We find that low-mass galaxies in low-density environments show higher Na I and DCO 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.
Abstract Copyright:
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Journal keyword(s):
galaxies: clusters: general - galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: formation - galaxies: stellar content
Simbad objects:
25
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