Research Note

Galaxy And Mass Assembly (GAMA): Galaxy colour gradients versus colour, structure, and luminosity

¹ School of Physics & Astronomy, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
e-mail: Rebecca.Kennedy@nottingham.ac.uk
² University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, Oxon OX1 3RH, UK
³ University of Hertfordshire, Hatfield, Hertfordshire AL10 9AB, UK
⁴ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
⁵ Australian Astronomical Observatory, PO Box 915, North Ryde, NSW 1670, Australia
⁶ University of Leiden, Sterrenwacht Leiden, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
⁷ IAASARS, National Observatory of Athens, 15236 Penteli, Greece
⁸ School of Physics, University of Melbourne, VIC 3010, Australia

Received: 14 April 2016
Accepted: 10 August 2016

Abstract

Using single-component fits to SDSS/UKIDSS images of galaxies in the G09 region of the GAMA survey we study radial colour gradients across the galaxy population. We use the multi-wavelength information provided by MegaMorph analysis of galaxy light profiles to calculate intrinsic colour gradients, and divide into six subsamples split by overall Sérsic index (n) and galaxy colour. We find a bimodality in the colour gradients of high- and low-n galaxies in all wavebands which varies with overall galaxy luminosity. Global trends in colour gradients therefore result from combining the contrasting behaviour of a number of different galaxy populations. The ubiquity of strong negative colour gradients supports the picture of inside-out growth through gas accretion for blue, low-n galaxies, and through dry minor mergers for red, high-n galaxies. An exception is the blue high-n population which has properties indicative of dissipative major mergers.