Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...183.4206g&link_type=abstract
American Astronomical Society, 183rd AAS Meeting, #42.06; Bulletin of the American Astronomical Society, Vol. 25, p.1355
Astronomy and Astrophysics
Astronomy
7
Scientific paper
We have measured a set of high-quality spectral indices for a sample of 40 normal elliptical galaxies. To study the stellar population in these systems, the line-strengths were measured with the Lick/IDS system and compared to model predictions for co-eval generations of stars as a function of age and metallicity. Strengths of features from species like Mg and Fe are not enough to separate age and metallicity of composite stellar populations. The age-metallicity degeneracy has been broken in this study by including the H_beta strength (an index more sensitive to age than metallicity). The H_beta strength varies considerably among the galaxies in contrast to the more metallicity-sensitive indices. The well defined light-strength patterns of the data reflect remarkable age-metallicity trends when compared to the models: although the mean stellar metallicity does not vary significantly among strong and weak-lined galaxies (Delta log /line{Z} ~ lt .18 dex), these two types of galaxies are separated by a considerable age spread. The strong H_beta absorption of weak-lined galaxies implies mean stellar ages as small as ~ 3-6 Gyr for these systems, in contrast to ages of ~ 12-15 Gyr in strong-lined galaxies. The Mg and Fe line-strength indices indicate a high [Mg/Fe] abundance ratio in strong-lined galaxies relative to the calibrating stars.
Faber Sandra M.
Gonzalez Jesús J.
Worthey Guy
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