Unbiased contaminant removal for 3D galaxy power spectrum measurements

Abstract

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, (iii) debiasing the resulting estimates. For (i), we show that removing the best-fit 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 $N_{\mathrm{mode}}^2$ matrices ($N_{\mathrm{mode}}$ 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 \citet*[FKP]{Feldman} 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.

10 pages, 4 figures; version equivalent to accepted article

References in corpus (6)

• Fast Estimators for Redshift-Space Clustering
• Measuring line-of-sight dependent Fourier-space clustering using FFTs
• Constraints on primordial non-Gaussianity from 800,000 photometric quasars
• The BigBOSS Experiment
• Exploiting the full potential of photometric quasar surveys: Optimal power spectra through blind mitigation of systematics
• Unbiased methods for removing systematics from galaxy clustering measurements

Cited by in corpus (10)

• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Growth rate of structure measurement from anisotropic clustering analysis in configuration space between redshift 0.6 and 1.1 for the Emission Line Galaxy sample
• Parameter constraints from cross-correlation of CMB lensing with galaxy clustering
• Improving Galaxy Clustering Measurements with Deep Learning: analysis of the DECaLS DR7 data
• Mitigating contamination in LSS surveys: a comparison of methods
• Primordial non-Gaussianity from the Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey I: Catalogue Preparation and Systematic Mitigation
• Unbiased pseudo-Cl power spectrum estimation with mode projection
• A map-based method for eliminating systematic modes from galaxy clustering power spectra with application to BOSS
• Measurement of the matter-radiation equality scale using the extended Baryon Oscillation Spectroscopic Survey Quasar Sample
• A blind method to recover the mask of a deep galaxy survey
• The Kaiser-Rocket effect: three decades and counting