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Galaxy And Mass Assembly (GAMA): understanding the wavelength dependence of galaxy structure with bulge-disc decompositions


Rebecca Kennedy


Ivan Baldry

Malcolm Bremer

Sarah Brough

Michael J.I. Brown

Simon Driver

Kenneth Duncan

Alister W. Graham

Benne W. Holwerda

Andrew M. Hopkins

Lee S. Kelvin

Rebecca Lange

Steven Phillipps

Marina Vika

Benedetta Vulcani


With a large sample of bright, low-redshift galaxies with optical–near-IR imaging from the GAMA survey we use bulge-disc decompositions to understand the wavelength-dependent behaviour of single-Sersic structural measurements. We denote the variation in single-Sersic index with wavelength as N, likewise for effective radius we use R. We find that most galaxies with a substantial disc, even those with no discernable bulge, display a high value of N. The increase in Sersic index to longer wavelengths is therefore intrinsic to discs, apparently resulting from radial variations in stellar population and/or dust reddening. Similarly, low values of R (< 1) are found to be ubiquitous, implying an element of universality in galaxy colour gradients. We also study how bulge and disc colour distributions vary with galaxy type. We find that, rather than all bulges being red and all discs being blue in absolute terms, both components become redder for galaxies with redder total colours. We even observe that bulges in bluer galaxies are typically bluer than discs in red galaxies, and that bulges and discs are closer in colour for fainter galaxies. Trends in total colour are therefore not solely due to the colour or flux dominance of the bulge or disc.


Kennedy, R., Bamford, S. P., Häußler, B., Baldry, I., Bremer, M., Brough, S., …Vulcani, B. (2016). Galaxy And Mass Assembly (GAMA): understanding the wavelength dependence of galaxy structure with bulge-disc decompositions. Monthly Notices of the Royal Astronomical Society, 460(4),

Journal Article Type Article
Acceptance Date May 13, 2016
Online Publication Date May 19, 2016
Publication Date Aug 21, 2016
Deposit Date Jul 13, 2016
Publicly Available Date Jul 13, 2016
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 460
Issue 4
Keywords galaxies: formation, galaxies: fundamental parameters, galaxies: general, galaxies: structure
Public URL
Publisher URL
Additional Information This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


MNRAS-2016-Kennedy-3458-71.pdf (3.4 Mb)

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