Galaxy And Mass Assembly (GAMA): Structural Investigation of Galaxies via Model Analysis (SIGMA)

Lee S. Kelvin, Simon P. Driver, Aaron S. G. Robotham, David T. Hill, Mehmet Alpaslan, Ivan K. Baldry, Steven P. Bamford, Joss Bland-Hawthorn, Sarah Brough, Alister W. Graham, Boris Häussler, Andrew M. Hopkins, Jochen Liske, Jon Loveday, Peder Norberg, Steven Phillipps, Cristina C. Popescu, Matthew Prescott, Edward N. Taylor, Richard J. Tuffs

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


We present single-S\'ersic two-dimensional model fits to 167,600 galaxies modelled independently in the ugrizYJHK bandpasses using reprocessed Sloan Digital Sky Survey Data Release Seven (SDSS DR7) and UKIRT Infrared Deep Sky Survey Large Area Survey (UKIDSS-LAS) imaging data available from the GAMA database. In order to facilitate this study we developed SIGMA, an R wrapper around several contemporary astronomy software packages including Source Extractor, PSF Extractor and GALFIT 3. SIGMA produces realistic 2D model fits to galaxies, employing automatic adaptive background subtraction and empirical PSF measurements on the fly for each galaxy in GAMA. Using these results, we define a common coverage area across the three GAMA regions containing 138,269 galaxies. We provide S\'ersic magnitudes truncated at 10 re which show good agreement with SDSS Petrosian and GAMA photometry for low S\'ersic index systems (n 4), recovering as much as \Delta m = 0.5 magnitudes in the r band. We employ a K band S\'ersic index/u - r colour relation to delineate the massive (n > ~2) early-type galaxies (ETGs) from the late-type galaxies (LTGs). The mean S\'ersic index of these ETGs shows a smooth variation with wavelength, increasing by 30% from g through K. LTGs exhibit a more extreme change in S\'ersic index, increasing by 52% across the same range. In addition, ETGs and LTGs exhibit a 38% and 25% decrease respectively in half-light radius from g through K. These trends are shown to arise due to the effects of dust attenuation and stellar population/metallicity gradients within galaxy populations.
Original languageUndefined/Unknown
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 8 Dec 2011

Bibliographical note

36 pages, 25 figures, accepted for publication in MNRAS (7 December 2011). High resolution version may be found at


  • astro-ph.CO
  • astro-ph.GA

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