%0 Journal Article
%4 sid.inpe.br/mtc-m19/2012/12.11.17.36
%2 sid.inpe.br/mtc-m19/2012/12.11.17.36.41
%@doi 10.1111/j.1365-2966.2012.21848.x
%@issn 1365-2966
%T SPIDER - VII. Revealing the stellar population content of massive early-type galaxies out to 8Re
%D 2012
%8 Nov.
%A La Barbera, F.,
%A Ferreras, I.,
%A Carvalho, R. R.,
%A Bruzual, G.,
%A Charlot, S.,
%A Pasquali, A.,
%A Merlin, E.,
%@affiliation INAF Osservatorio Astron Capodimonte, Naples, Italy.
%@affiliation Univ Coll London, MSSL, Dorking RH5 6NT, Surrey, England
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Univ Nacl Autonoma Mexico, Ctr Radioastron & Astrofis, Mexico City, DF, Mexico
%@affiliation UPMC, Inst Astrophys Paris, UMR7095, F-75014 Paris, France
%@affiliation Univ Heidelberg, Zentrum Astron, Astron Rechen Inst, D-69120 Heidelberg, Germany
%@affiliation INAF Osservatorio Astron Padova, Padua, Italy
%B Monthly Notices of the Royal Astronomical Society
%V 426 10.1111/j.1365-2966.2012.21848.x
%N 3
%P 2300 - 2317
%K elliptical and lenticular galaxies, cD, galaxy evolution, galaxy formation, stellar content.
%X Radial trends of stellar populations in galaxies provide a valuable tool to understand the mechanisms of galaxy growth. In this paper, we present the first comprehensive analysis of opticaloptical and opticalNIR colours, as a function of galaxy mass, out to the halo region (8Re) of early-type galaxies (ETGs). We select a sample of 674 massive ETGs (M⋆> 3 × 1010M⊙) from the SDSS-based SPIDER survey. By com-paring with a large range of population synthesis models, we derive robust constraints on the radial trends in age and metallicity. Metallicity is unambiguously found to decrease outwards, with a measurable steepening of the slope in the outer regions (Re < R < 8Re). The gradients in stellar age are found to be more sensitive to the models used, but in general, the outer regions of ETGs feature older populations compared to the cores. This trend is strongest for the most massive galaxies in our sample (M⋆> 1011M⊙). Furthermore, when segregating with respect to large scale environment, the age gradient is more significant in ETGs residing in higher density regions. These results shed light on the processes leading from the formation of the central core to the growth of the stellar envelope of massive galaxies. The fact that the populations in the outer regions are older and more metal-poor than in the core suggests a process whereby the envelope of massive galaxies is made up of accreted small satellites (i.e. minor mergers) whose stars were born during the first stages of galaxy formation.
%@language en