Impact of thermal Sunyaev–Zeldovich effect on cross-correlations between Planck cosmic microwave background lensing and SDSS galaxy density fields. Issue 1 (24th May 2022)

• Record Type: Journal Article
• Authors: Chen, Tianyue; Remazeilles, Mathieu
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 514:Issue 1(2022)
• Page Start: 596
• Page End: 606
• Publication Date: 2022-05-24
• Subjects: (cosmology:) cosmic background radiation -- (cosmology:) large-scale structure of Universe -- galaxies: clusters: general -- methods: data analysis -- methods: statistical; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac1436
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Residual foreground contamination by thermal Sunyaev–Zeldovich (tSZ) effect from galaxy clusters in cosmic microwave background (CMB) maps propagates into the reconstructed CMB lensing field, and thus biases the intrinsic cross-correlation between CMB lensing and large-scale structure (LSS). Through stacking analysis, we show that residual tSZ contamination causes an increment of lensing convergence in the central part of the clusters and a decrement of lensing convergence in the cluster outskirts. We quantify the impact of residual tSZ contamination on cross-correlations between the Planck 2018 CMB lensing convergence maps and the Sloan Digital Sky Survey-IV galaxy density data through cross-power spectrum computation. In contrast with the Planck 2018 tSZ-deprojected smica lensing map, our analysis using the tSZ-contaminated smica lensing map measures an $\sim\!2.5{{\ \rm per\, cent}}$ negative bias at multipoles ℓ ≲ 500 and transits to an $\sim\!9{{\ \rm per\, cent}}$ positive bias at ℓ ≳ 1500, which validates earlier theoretical predictions of the overall shape of such tSZ-induced spurious cross-correlation. The tSZ-induced lensing convergence field in Planck CMB data is detected with more than 1σ significance at ℓ ≲ 500 and more than 14σ significance at ℓ ≳ 1500, yielding an overall 14.8σ detection. We also show that masking galaxy clusters in CMB data is not sufficient to eliminate the spurious lensing signal, still detecting a non-negligible bias with 5.5σ significance on cross-correlations with galaxy density fields. Our results emphasize how essential it is to deproject the tSZ effect from CMB maps at the component separation stage and adopt tSZ-free CMB lensing maps for cross-correlations with LSS data.