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

Rebecca Kennedy, Steven Bamford, Boris Haussler, Ivan K. Baldry, Malcolm Bremer, Sarah Brough, Michael Brown, Simon Driver, Kenneth Duncan, Alister Graham, Benne Holwerda, Andrew Hopkins, Lee Kelvin, Rebecca Lange, Steven Phillipps, Marina Vika, Benedetta Vulcani

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)
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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 behavior of single-Sérsic structural measurements. We denote the variation in single-Sérsic 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 Sérsic 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.
Original languageEnglish
Pages (from-to)3458-3471
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date19 May 2016
Publication statusPublished - 21 Aug 2016


  • galaxies: formation
  • galaxies: fundamental parameters
  • galaxies: general
  • galaxies: structure


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