Eight luminous early-type galaxies in nearby pairs and sparse groups. I. Stellar populations spatially analysed |
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| Authors: | D A Rosa A C Milone A C Krabbe I Rodrigues |
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| Institution: | 1.Divis?o de Astrofísica,Instituto Nacional de Pesquisas Espaciais,S?o José dos Campos,Brazil;2.Instituto de Pesquisa & Desenvolvimento,Universidade do Vale do Paraíba,S?o José dos Campos,Brazil |
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| Abstract: | We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may have interaction with another galaxy of similar mass. We have spatially measured luminosity-weighted averages of age, M/H], Fe/H], and \(\alpha /\mbox{Fe}\)] in the sample galaxies to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the well-established stellar population synthesis code starlight using semi-empirical simple stellar population models. Radial variations of luminosity- weighted means of age, M/H], Fe/H], and \(\alpha /\mbox{Fe}\)] were quantified up to half of the effective radius of each galaxy. We found trends between representative values of age, M/H], \(\alpha /\mbox{Fe}\)], and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1–4 Gyr old stellar populations were quantified in IC?5328 and NGC?6758 as well as 4–8 Gyr old ones in NGC?5812. Extended gas is present in IC?5328, NGC?1052, NGC?1209, and NGC?6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are basically dominated by \(\alpha \)-enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and \(\alpha /\mbox{Fe}\)] gradients are null and the M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass cannot be discarded in the formation and evolution of early-type galaxies. |
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