Journal Article

Astrophysically motivated bulge–disc decompositions of Sloan Digital Sky Survey galaxies

C. N. Lackner and J. E. Gunn

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 3, pages 2277-2302
Published in print April 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20450.x
Astrophysically motivated bulge–disc decompositions of Sloan Digital Sky Survey galaxies

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We present a set of bulge–disc decompositions for a sample of 71 825 Sloan Digital Sky Survey (SDSS) main-sample galaxies in the redshift range 0.003 < z < 0.05. We have fitted each galaxy with either a de Vaucouleurs (‘classical’) or an exponential (‘pseudo-’) bulge and an exponential disc. Two-dimensional Sérsic fits are performed when the two-component fits are not statistically significant or when the fits are poor, even in the presence of high signal-to-noise ratio (S/N). We study the robustness of our two-component fits by studying a bright subsample of galaxies and we study the systematics of these fits with decreasing resolution and S/N. Only 30 per cent of our sample have been fitted with two-component fits in which both components are non-zero. The gr and gi colours of each component for the two-component models are determined using linear templates derived from the r-band model. We attempt a physical classification of types of fits into disc galaxies, pseudo-bulges, classical bulges and ellipticals. Our classification of galaxies agrees well with previous large bulge plus disc (B+D) decomposed samples. Using our galaxy classifications, we find that Petrosian concentration is a good indicator of bulge-to-total ratio, while overall Sérsic index is not. Additionally, we find that the majority of green valley galaxies are bulge+disc galaxies. Furthermore, in the transition from green to red B+D galaxies, the total galaxy colour is most strongly correlated with the disc colour.

Keywords: galaxies: bulges; galaxies: evolution; galaxies: photometry; galaxies: structure

Journal Article.  18261 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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