Making maps of cosmological parameters

TL;DR

This paper introduces a fast, efficient algorithm to create maps of local cosmological parameters, enabling the detection of directional dependencies and local variations in cosmological data.

Contribution

The paper presents a novel quadratic estimator technique based on Wiener filtering for mapping local cosmological parameters from full or partial sky data.

Findings

Planck data is consistent with a single global cosmological parameter value.

The method efficiently detects local variations or contaminations in cosmological data.

Applicable to future missions for detailed local cosmological analysis.

Abstract

We provide a fast algorithm to diagnose any directional dependence in the cosmological parameters by calculating maps of local cosmological parameter estimates and their joint errors. The technique implements a fast quadratic estimator technique based on Wiener filtering and convolution of the sky with a patch shape. It uses only three map-resolution spherical harmonic transforms per parameter and applies to any data set with full sky or a partial sky coverage. We apply this method to Planck SMICA-2015 and obtain fluctuation map for six cosmological parameters. Our estimate shows that the Planck data is consistent with a single global value of the cosmological parameters and is not influenced by any severe local contaminations. This method is applicable also to other angular or 3D data sets of future missions to scrutinize any local variation in the cosmological parameters.