An Assessment of Contamination in the thermal-SZ Map Using Cross Correlations

TL;DR

This study assesses contamination in the Planck tSZ map by analyzing cross-correlations with lensing and CMB data, finding that CIB contamination is minimal while galactic dust has negligible impact on the tSZ-lensing signal.

Contribution

It introduces a method to evaluate contamination sources in the tSZ map using cross-correlation techniques with lensing and CMB data.

Findings

CIB contributes about 7.5% to the cross-correlation signal, confirming robustness of previous detections.

Planck NILC tSZ cross CMB lensing is biased by approximately 18%.

Galactic dust does not significantly affect the tSZ-lensing cross-correlation.

Abstract

We search for the potential contamination in the Planck thermal Sunyaev-Zeldovich (tSZ) map by calculating the cross-correlation between the tSZ signal and weak lensing by large scale structure and the Cosmic Microwave Background (CMB). The lensing data we use is the convergence map from the Red Sequence Cluster Lensing Survey (RCSLens) and the Planck CMB lensing map. We reconstruct the tSZ $y$ map with a Needlet Internal Linear Combination method using the HFI sky maps from the Planck satellite. We remove the CMB signal while minimizing the residual noise. The cross correlation signal from our reconstructed $y$ map is consistent with that from the Planck team's NILC $y$ map. The CIB and galactic dust emission are two potential sources of contamination in the reconstructed $y$ map. We remove the CIB signal by subtracting the CIB maps reconstructed by Planck collaboration from the raw temperature maps. We find that cross-correlation between the CIB and galactic lensing contributes to $(7.5\pm6.0)\%$ in the Planck NILC tSZ cross galactic lensing signal within $100<\ell<2000$, which implies that previous detections of the tSZ cross galactic lensing is robust to CIB contaminations. In contrast, the Planck NILC tSZ cross CMB lensing is biased by $(18.4\pm2.8)\%$ in the same $\ell$ range. Galactic dust contamination is tested by projecting out a grey-body dust models with different dust spectral indices. Galactic dust does not affect galactic lensing cross tSZ signal significantly.