Observational hints of radial migration in disc galaxies from CALIFA^⋆,⋆⋆

¹ Departamento de Física Teórica y del CosmosUniversidad de Granada, Campus de Fuentenueva, 18071 Granada, Spain
e-mail: tomasruizlara@gmail.com
² Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071 Granada, Spain
³ Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁴ Departamento de Astrofísica, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain
⁵ Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Cantoblanco, Spain
⁶ School of Physics and Astronomy, University of St Andrews, SUPA, North Haugh, KY16 9 SS St Andrews, UK
⁷ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, Aptdo. 3004, 18080 Granada, Spain
⁸ Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510 México D.F., Mexico
⁹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
¹⁰ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹¹ Department of Physics, Institute for Astronomy, ETH Zürich, 8093 Zürich, Switzerland
¹² Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹³ Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹⁴ Sydney Institute for Astronomy, School of Physics A28, University of Sydney, Sydney, NSW 2006, Australia
¹⁵ PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
¹⁶ Observatorio Astronómico, Laprida 854, 5000 BGR Córdoba, Argentina
¹⁷ Consejo de Investigaciones Científicas y Técnicas de la República Argentina, Avda. Rivadavia 1917, 1033 AAJ CABA, Argentina
¹⁸ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹⁹ INAF–Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
²⁰ University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria

Received: 27 February 2017
Accepted: 3 May 2017

Abstract

Context. According to numerical simulations, stars are not always kept at their birth galactocentric distances but they have a tendency to migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if radial migration is indeed important, galaxies with different surface brightness (SB) profiles must display differences in their stellar population properties.

Aims. We investigate the role of radial migration in the light distribution and radial stellar content by comparing the inner colour, age, and metallicity gradients for galaxies with different SB profiles. We define these inner parts, avoiding the bulge and bar regions and up to around three disc scale lengths (type I, pure exponential) or the break radius (type II, downbending; type III, upbending).

Methods. We analysed 214 spiral galaxies from the CALIFA survey covering different SB profiles. We made use of GASP2D and SDSS data to characterise the light distribution and obtain colour profiles of these spiral galaxies. The stellar age and metallicity profiles were computed using a methodology based on full-spectrum fitting techniques (pPXF, GANDALF, and STECKMAP) to the Integral Field Spectroscopic CALIFA data.

Results. The distributions of the colour, stellar age, and stellar metallicity gradients in the inner parts for galaxies displaying different SB profiles are unalike as suggested by Kolmogorov-Smirnov and Anderson-Darling tests. We find a trend in which type II galaxies show the steepest profiles of all, type III show the shallowest, and type I display an intermediate behaviour.

Conclusions. These results are consistent with a scenario in which radial migration is more efficient for type III galaxies than for type I systems, where type II galaxies present the lowest radial migration efficiency. In such a scenario, radial migration mixes the stellar content, thereby flattening the radial stellar properties and shaping different SB profiles. However, in light of these results we cannot further quantify the importance of radial migration in shaping spiral galaxies, and other processes, such as recent star formation or satellite accretion, might play a role.