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Título              : Strong Balmer lines in old stellar populations: no need for young ages in ellipticals?  
Conferencista: Claudia Maraston, Universitäts-Sternwarte München, Germany  
Data                : Segunda-Feira 29/01/01  
Local               : Auditório L.B.F. Clauzet - Água Funda  
Sumário         :
Comparing models of simple Stellar Populations (SSP) with observed line strengths generally provides a tool to break the age-metallicity degeneracy in elliptical galaxies. Due to the wide range of Balmer line strenghts observed, ellipticals have been interpreted to exhibit an appreciable scatter in age. In this paper, we analyze Composite Stellar Population models with a simple mix of an old metal-rich and an old metal-poor component. We show that these models simultaneously produce strong Balmer lines and strong metallic lines without invoking a young population. The key to this result is that our model are based on SSPs that better match the steep increase oh Hbeta in the literature. Hence, the scatter of Hbeta observed in cluster and lumunous field galaxies can be explained by a spread in the metallicity of old stellar populations. We check our model with respect to the so-called G-dwarf problem in ellipticals. For a galaxy subsample covering a large range in UV-V colors we demonstrate that the addition of an old metal-poor subcomponent does not invalidate other observational constraints like colors and the flux in the mid-UV.