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

摘要

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.