Galaxy and Mass Assembly: FUV, NUV, ugrizYJHK Petrosian, Kron and Sersic photometry

David T. Hill*, Lee S. Kelvin, Simon P. Driver, Aaron S. G. Robotham, Ewan Cameron, Nicholas Cross, Ellen Andrae, Ivan K. Baldry, Steven P. Bamford, Joss Bland-Hawthorn, Sarah Brough, Christopher J. Conselice, Simon Dye, Andrew M. Hopkins, Jochen Liske, Jon Loveday, Peder Norberg, John A. Peacock, Scott M. Croom, Carlos S. FrenkAlister W. Graham, D. Heath Jones, Konrad Kuijken, Barry F. Madore, Robert C. Nichol, Hannah R. Parkinson, Steven Phillipps, Kevin A. Pimbblet, Cristina C. Popescu, Matthew Prescott, Mark Seibert, Rob G. Sharp, Will J. Sutherland, Daniel Thomas, Richard J. Tuffs, Elco van Kampen

*Corresponding author for this work

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

109 Citations (Scopus)


In order to generate credible 0.1-2 mu m spectral energy distributions, the Galaxy and Mass Assembly (GAMA) project requires many gigabytes of imaging data from a number of instruments to be reprocessed into a standard format. In this paper, we discuss the software infrastructure we use, and create self-consistent ugrizYJHK photometry for all sources within the GAMA sample. Using UKIDSS and SDSS archive data, we outline the pre-processing necessary to standardize all images to a common zero-point, the steps taken to correct for the seeing bias across the data set and the creation of gigapixel-scale mosaics of the three 4 x 12 deg2 GAMA regions in each filter. From these mosaics, we extract source catalogues for the GAMA regions using elliptical Kron and Petrosian matched apertures. We also calculate Sersic magnitudes for all galaxies within the GAMA sample using sigma, a galaxy component modelling wrapper for galfit 3. We compare the resultant photometry directly and also calculate the r-band galaxy luminosity function for all photometric data sets to highlight the uncertainty introduced by the photometric method. We find that (1) changing the object detection threshold has a minor effect on the best-fitting Schechter parameters of the overall population (M* +/- 0.055 mag, alpha +/- 0.014, phi* +/- 0.0005 h3 Mpc-3); (2) there is an offset between data sets that use Kron or Petrosian photometry, regardless of the filter; (3) the decision to use circular or elliptical apertures causes an offset in M* of 0.20 mag; (4) the best-fitting Schechter parameters from total-magnitude photometric systems (such as SDSS modelmag or Sersic magnitudes) have a steeper faint-end slope than photometric systems based upon Kron or Petrosian measurements; and (5) our Universe's total luminosity density, when calculated using Kron or Petrosian r-band photometry, is underestimated by at least 15 per cent.

Original languageEnglish
Pages (from-to)765-799
Number of pages35
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Apr 2011


  • methods: data analysis
  • methods: observational
  • techniques: image processing
  • techniques: photometric
  • surveys
  • galaxies: fundamental parameters

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