Stellar population gradients in galaxy discs from the CALIFA survey^⋆

The influence of bars

¹ Departamento de Física TeóricaUniversidad Autónoma de Madrid, 28049 Cantoblanco, Spain
e-mail: p.sanchezblazquez@uam.es
² Instituto Nacional de Astrofísica, Óptica y Electrónica, 72840 Tonantzintla, Puebla, México
³ School of Physics & Astronomy, University of St Andrews, UK
⁴ Departamento de Física y del Cosmos, Universidad de Granada, 18071 Granada, Spain
⁵ Centro Astronómico Hispano Alemán de Calar Alto (CSIC-MPIA), 4004 Almería, Spain
⁶ Instituto de Astronomía,Universidad Nacional Autonóma de Mexico, A.P. 70-264, 04510 Mexico DF, Mexico
⁷ Istituto de Astrofísica de Andalucía (IAA-CSIC), 18080 Granada, Spain
⁸ INAF-Osservatorio Astrofisico di Arcetri - Largo Enrico Fermi 5, 50125 Firenze, Italy
⁹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Spain
¹⁰ Institute of Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006, Australia
¹¹ Departamento de Astrofísica y Ciencias de la Atmósfera, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹² Departamento de Física, Universidade Federal de Santa Catarina, PO Box 476, 88040-900, Florianópolis, SC, Brazil
¹³ Astronomical Institute, Academy of Science of the Czech Republic, Bocní 1401/1a, 14100 Prague, Czech Republic
¹⁴ Instituto de Cosmologia, Relatividade e Astrofísica ICRA, Centro Brasileiro de Pesquisas Físicas, Rua Dr.Xavier Sigaud 150, CEP 22290-180 Rio de Janeiro, RJ, Brazil
¹⁵ Departamento de Investigación Básica, CIEMAT, Avd Complutense 40, 28040 Madrid, Spain
¹⁶ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁷ Max-Planck-Institut für Astronomie, 69117 Heidelberg, Germany
¹⁸ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Postdam, Germany

Received: 13 February 2014
Accepted: 25 June 2014

Abstract

While studies of gas-phase metallicity gradients in disc galaxies are common, very little has been done towards the acquisition of stellar abundance gradients in the same regions. We present here a comparative study of the stellar metallicity and age distributions in a sample of 62 nearly face-on, spiral galaxies with and without bars, using data from the CALIFA survey. We measure the slopes of the gradients and study their relation with other properties of the galaxies. We find that the mean stellar age and metallicity gradients in the disc are shallow and negative. Furthermore, when normalized to the effective radius of the disc, the slope of the stellar population gradients does not correlate with the mass or with the morphological type of the galaxies. In contrast to this, the values of both age and metallicity at ~2.5 scale lengths correlate with the central velocity dispersion in a similar manner to the central values of the bulges, although bulges show, on average, older ages and higher metallicities than the discs. One of the goals of the present paper is to test the theoretical prediction that non-linear coupling between the bar and the spiral arms is an efficient mechanism for producing radial migrations across significant distances within discs. The process of radial migration should flatten the stellar metallicity gradient with time and, therefore, we would expect flatter stellar metallicity gradients in barred galaxies. However, we do not find any difference in the metallicity or age gradients between galaxies with and without bars. We discuss possible scenarios that can lead to this lack of difference.