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No direct coupling between bending of galaxy disc stellar age and light profiles

T. Ruiz-Lara, I. Pérez, E. Florido, P. Sánchez-Blázquez, J. Méndez-Abreu, M. Lyubenova, J. Falcón-Barroso, L. Sánchez-Menguiano, S. F. Sánchez, L. Galbany, R. García-Benito, R. M. González Delgado, B. Husemann, C. Kehrig, Á. R. López-Sánchez, R. A. Marino, D. Mast, P. Papaderos, G. van de Ven, C. J. Walcher, S. Zibetti, and the CALIFA collaboration

We study the stellar properties of 44 face-on spiral galaxies from the Calar Alto Legacy Integral Field Area survey via full spectrum fitting techniques. We compare the age profiles with the surface brightness distribution in order to highlight differences between profile types (type I, exponential profile; and II, down-bending profile). We observe an upturn (`U-shape') in the age profiles for 17 out of these 44 galaxies with reliable stellar information up to their outer parts. This `U-shape' is not a unique feature for type II galaxies but can be observed in type I as well. These findings suggest that the mechanisms shaping the surface brightness and stellar population distributions are not directly coupled. This upturn in age is only observable in the light-weighted profiles while it flattens out in the mass-weighted profiles. Given recent results on the outer parts of nearby systems and the results presented in this Letter, one of the most plausible explanations for the age upturn is an early formation of the entire disc (~10 Gyr ago) followed by an inside-out quenching of the star formation.

techniques: spectroscopic, galaxies: evolution, galaxies: formation, galaxies: spiral, galaxies: stellar content, galaxies: structure

Monthly Notices of the Royal Astronomical Society
Volume 456, Issue 4, Page L35
2016 February

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia