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Date and Time of the Query: 2019-03-20 T14:55:15 PDT
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For refcode 2006A&A...457..787S:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2006A&A...457..787S Stellar populations of early-type galaxies in different environments. I. Line-strength indices. Relations of line-strengths with {sigma} Sanchez-Blazquez, P.; Gorgas, J.; Cardiel, N.; Gonzalez, J. J. Abstract. Aims. This paper commences a series devoted to the study of the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. Methods: In this paper we describe the details of the galaxy sample, the observations, and the data reduction. Line-strength indices and velocity dispersions ({sigma}) are measured in 98 early-type galaxies drawn from different environments, and the relation of the indices with the velocity dispersion analysed in detail. Results: The present sample indicates that some of the index-{sigma} relations depend on galaxy environment. In particular, the slope of the relation between Balmer lines and {sigma} is steeper for galaxies in the Virgo cluster, small groups, and in the field than for galaxies in the Coma cluster. In several indices there is also a significant offset in the zero point between the relations defined by the different subsamples. The slopes of the index-{sigma} relation for the Virgo and low-density environment galaxies are explained by a variation of both age and metallicity, with velocity dispersion, as previously noted in other studies. For the galaxies in the Coma cluster, however, the relation of the indices with {sigma} only requires a variation of the abundance along the {sigma} sequence. In agreement with other studies, we find that the models that better reproduce the slopes are those in which the {alpha} elements vary more than the Fe-peak elements along the {sigma} sequence, while, at a given {sigma}, older galaxies show an higher {alpha}/Fe ratio. Conclusions: The results can be explained assuming that galaxies in the Coma cluster have experienced a truncated star formation and chemical enrichment history compared to a more continuous time-extended history for their counterparts in lower density environments. Key words: galaxies: evolution, galaxies: elliptical and, lenticular, cD, galaxies: stellar content
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