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Physics and Astronomy


We derive single Sérsic fits and bulge-disc decompositions for 13 096 galaxies at redshifts z < 0.08 in the GAMA II equatorial survey regions in the Kilo-Degree Survey (KiDS) g, r, and i bands. The surface brightness fitting is performed using the Bayesian two-dimensional profile fitting code PROFIT. We fit three models to each galaxy in each band independently with a fully automated Markov chain Monte Carlo analysis: a single Sérsic model, a Sérsic plus exponential and a point source plus exponential. After fitting the galaxies, we perform model selection and flag galaxies for which none of our models are appropriate (mainly mergers/Irregular galaxies). The fit quality is assessed by visual inspections, comparison to previous works, comparison of independent fits of galaxies in the overlap regions between KiDS tiles and bespoke simulations. The latter two are also used for a detailed investigation of systematic error sources. We find that our fit results are robust across various galaxy types and image qualities with minimal biases. Errors given by the MCMC underestimate the true errors typically by factors 2–3. Automated model selection criteria are accurate to >90 per cent" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant: inherit; font-stretch: inherit; line-height: normal; font-family: inherit; vertical-align: baseline; display: inline; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">>90 per cent>90 per cent as calibrated by visual inspection of a subsample of galaxies. We also present gr component colours and the corresponding colour–magnitude diagram, consistent with previous works despite our increased fit flexibility. Such reliable structural parameters for the components of a diverse sample of galaxies across multiple bands will be integral to various studies of galaxy properties and evolution. All results are integrated into the GAMA database.


© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society

Original Publication Information

Sarah Casura, Jochen Liske, Aaron S G Robotham, Sarah Brough, Simon P Driver, Alister W Graham, Boris Häußler, Benne W Holwerda, Andrew M Hopkins, Lee S Kelvin, Amanda J Moffett, Dan S Taranu, Edward N Taylor, Galaxy And Mass Assembly (GAMA): bulge-disc decomposition of KiDS data in the nearby Universe, Monthly Notices of the Royal Astronomical Society, Volume 516, Issue 1, October 2022, Pages 942–974.