Journal Article

Completeness – II. A signal-to-noise ratio approach for completeness estimators applied to galaxy magnitude–redshift surveys

Luís Teodoro, Russell Johnston and Martin Hendry

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 405, issue 2, pages 1187-1194
Published in print June 2010 | ISSN: 0035-8711
Published online June 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16580.x
Completeness – II. A signal-to-noise ratio approach for completeness estimators applied to galaxy magnitude–redshift surveys

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This is the second paper in our completeness series, which addresses some of the issues raised in the previous article by Johnston, Teodoro & Hendry, in which we developed statistical tests for assessing the completeness in apparent magnitude of magnitude–redshift surveys defined by two flux limits. The statistics, Tc and Tv, associated with these tests are non-parametric and defined in terms of the observed cumulative distribution function of sources; they represent powerful tools for identifying the true flux limit and/or characterizing systematic errors in magnitude–redshift data.

In this paper, we present a new approach to constructing these estimators that resembles an ‘adaptive smoothing’ procedure – i.e. by seeking to maintain the same amount of the information, as measured by the signal-to-noise ratio (S/N), allocated to each galaxy. For consistency with our previous work, we apply our improved estimators to the Millennium Galaxy Catalogue and the 2dF Galaxy Redshift Survey data, and demonstrate that one needs to use an S/N appropriately tailored for each individual catalogue to optimize the performance of the completeness estimators. Furthermore, unless such an adaptive procedure is employed, the assessment of completeness may result in a spurious outcome if one uses other estimators present in the literature which have not been designed taking into account ‘shot-noise’ due to sampling.

Keywords: methods: data analysis; methods: statistical; astronomical data bases: miscellaneous; galaxies: statistics; large-scale structure of Universe

Journal Article.  6161 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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