The Stellar Populations of Early-Type Galaxies in the Fornax Cluster |
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Authors: | H Kuntschner |
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Institution: | (1) Department of Physics, University of Durham, South Rd, Durham, DH1 3LE, UK |
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Abstract: | We have measured central line strengths for a complete sample of early-type galaxies in the Fornax Cluster comprising 11 elliptical
and 11 lenticular galaxies, more luminous than M
B=–17. We find that the centres of Fornax ellipticals follow the locus of galaxies of fixed age in Worthey's models and have
metallicities varying roughly from half to 2.5 times solar. The centres of (relatively low luminosity) lenticular galaxies,
however, exhibit a substantial spread to younger luminosity-weighted ages indicating amore extended star formation history.
Our conclusions are based on two age/metallicity diagnostic diagrams in the Lick/IDS system comprising established indices
such as MgFe]and Hβ as well as new and more sensitive indices, such as Fe3and H
. The inferred difference in the age distribution between lenticular and elliptical galaxies is a robust conclusion as the
models generate consistent relative ages using different age and metallicity indicators even though the absolute ages remain
uncertain. The absolute age uncertainty is caused mainly by the effects of non-solar abundance ratios, which are not accounted
for in the stellar population models. We find that Es are generally overabundant in magnesium and the most luminous galaxies
show stronger overabundances. The luminosity-weighted stellar populations of young S0s are consistent with solar abundance
ratios or a weak Mg under abundance. Two of the faintest lenticular galaxies in our sample have blue continua and extremely
strong Balmer-line absorptions suggesting starbursts <2 Gyr ago.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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