Bibcode
Mármol-Queraltó, E.; Cardiel, N.; Sánchez-Blázquez, P.; Trager, S. C.; Peletier, R. F.; Kuntschner, H.; Silva, D. R.; Cenarro, A. J.; Vazdekis, A.; Gorgas, J.
Referencia bibliográfica
The Astrophysical Journal Letters, Volume 705, Issue 2, pp. L199-L203 (2009).
Advertised on:
11
2009
Número de citas
28
Número de citas referidas
24
Descripción
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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