期刊
ASTRONOMY & ASTROPHYSICS
卷 482, 期 3, 页码 1053-1067出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361:20066601
关键词
techniques : image processing; methods : data analysis; techniques : photometric; galaxies : fundamental parameters
Aims. We describe a new technique for measuring accurate galaxy colours from images taken under different seeing conditions. Methods. The method involves two ingredients. First we define the Gaussian-aperture-and-PSF flux, which is the Gaussian-weighted flux a galaxy would have if it were observed with a Gaussian PSF. This theoretical aperture flux is independent of the PSF or pixel scale that the galaxy was observed with. Second we develop a procedure for measuring such a GaaP flux from observed, pixellated images. This involves modelling source and PSF as a superposition of orthogonal shapelets. A correction scheme is also described that approximately corrects for any residuals to the shapelet expansions. Results. A series of tests on simulated images shows that it is possible with this method to reduce systematic errors in the matched-aperture fluxes to the level of one percent, which makes it useful for deriving photometric redshifts from large imaging surveys.
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