An improved Compton parameter map of thermal Sunyaev-Zeldovich effect from Planck PR4 data

TL;DR

This paper presents a new, high-quality all-sky Compton-$y$ map of the thermal Sunyaev-Zeldovich effect derived from the latest Planck PR4 data, showing improvements over previous versions in noise reduction and contamination mitigation.

Contribution

The authors develop and validate a tailored NILC pipeline to produce an improved PR4 $y$-map, reducing noise and systematic contamination compared to the PR2 release.

Findings

Reduced large-scale noise and systematics in the PR4 $y$-map.

Lower residual contamination near the Galactic plane.

Decreased thermal noise and CIB contamination at small scales.

Abstract

Taking advantage of the reduced levels of noise and systematics in the data of the latest Planck release (PR4, also known as NPIPE), we construct a new all-sky Compton-$y$ parameter map (hereafter, $y$-map) of the thermal Sunyaev-Zeldovich (SZ) effect from the Planck PR4 data. A tailored Needlet Internal Linear Combination (NILC) pipeline, first validated on detailed sky simulations, is applied to the nine single-frequency Planck PR4 sky maps, ranging from $30$ to $857$ GHz, to produce the PR4 $y$-map over 98% of the sky. Using map comparisons, angular power spectra and one-point statistics we show that the PR4 NILC $y$-map is of improved quality compared to that of the previous PR2 release. The new $y$-map shows reduced levels of large-scale striations associated with $1/f$ noise in the scan direction. Regions near the Galactic plane also show lower residual contamination by Galactic thermal dust emission. At small angular scales, the residual contamination by thermal noise and cosmic infrared background (CIB) emission is found to be reduced by around 7% and 34%, respectively, in the PR4 $y$-map. The PR4 NILC $y$-map is made publicly available for astrophysical and cosmological analyses of the thermal SZ effect.