Unbiased contaminant removal for 3D galaxy power spectrum measurements

Journal Article · Mon Aug 15 00:00:00 EDT 2016 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stw2008· OSTI ID:1532929

Kalus, B. ^[1]; Percival, W. J. ^[1]; Bacon, D. J. ^[1]; Samushia, L. ^[2]

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1. Univ. of Portsmouth (United Kingdom)
2. Univ. of Portsmouth (United Kingdom); Kansas State Univ., Manhattan, KS (United States); Ilia State University, Tbilisi (Georgia)

In this work, we assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum and (iii) debiasing the resulting estimates. For (i), we show that removing the best-fitting contaminant (mode subtraction) and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a quadratic maximum likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large $$N^2_{\text{mode}}$$ matrices ($$N_{\text{mode}}$$ being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants, is less severe than that commonly ignored due to the survey window.

• Research Organization: Kansas State Univ., Manhattan, KS (United States)
• Sponsoring Organization: USDOE Office of Science (SC); Science and Technology Facilities Council (STFC); European Research Council (ERC); Swiss National Science Foundation (SNF); Georgia National Science Foundation (GNSF)
• Grant/Contract Number: FG03-99ER41093; ST/K0090X/1; ST/N00180X/1; SCOPES IZ73Z0-152581
• OSTI ID: 1532929
• Journal Information: Monthly Notices of the Royal Astronomical Society, Vol. 463, Issue 1; ISSN 0035-8711
• Publisher: Royal Astronomical Society
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Astronomy & Astrophysics
methods: statistical
large-scale structure of Universe