Elsner, F;
Leistedt, B;
Peiris, HV;
(2016)
Unbiased methods for removing systematics from galaxy clustering measurements.
Monthly Notices Of The Royal Astronomical Society
, 456
(2)
pp. 2095-2104.
10.1093/mnras/stv2777.
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Abstract
Measuring the angular clustering of galaxies as a function of redshift is a powerful method for extracting information from the three-dimensional galaxy distribution. The precision of such measurements will dramatically increase with ongoing and future wide-field galaxy surveys. However, these are also increasingly sensitive to observational and astrophysical contaminants. Here, we study the statistical properties of three methods proposed for controlling such systematics – template subtraction, basic mode projection, and extended mode projection – all of which make use of externally supplied template maps, designed to characterize and capture the spatial variations of potential systematic effects. Based on a detailed mathematical analysis, and in agreement with simulations, we find that the template subtraction method in its original formulation returns biased estimates of the galaxy angular clustering. We derive closed-form expressions that should be used to correct results for this shortcoming. Turning to the basic mode projection algorithm, we prove it to be free of any bias, whereas we conclude that results computed with extended mode projection are biased. Within a simplified setup, we derive analytical expressions for the bias and discuss the options for correcting it in more realistic configurations. Common to all three methods is an increased estimator variance induced by the cleaning process, albeit at different levels. These results enable unbiased high-precision clustering measurements in the presence of spatially varying systematics, an essential step towards realizing the full potential of current and planned galaxy surveys.
| Type: | Article |
|---|---|
| Title: | Unbiased methods for removing systematics from galaxy clustering measurements |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stv2777 |
| Publisher version: | http://dx.doi.org/10.1093/mnras/stv2777 |
| Language: | English |
| Additional information: | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. Copyright © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society |
| Keywords: | methods: data analysis, methods: numerical, methods: statistical, cosmology: observations, large-scale structure of Universe |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1492629 |
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