# Predicting the CIB-$\phi$ contamination in the cross-correlation of the tSZ effect and $\phi$

## TL;DR

This paper assesses the contamination of cosmic infrared background (CIB) fluctuations on the cross-correlation between the thermal Sunyaev-Zel'dovich effect and the CMB lensing potential, revealing significant biases in current analyses.

## Contribution

It provides an estimation of CIB-$$ contamination in tSZ-$$ cross-correlation using Planck data, highlighting the limitations of current Compton parameter maps.

## Key findings

- CIB-$$ contamination is significant relative to the tSZ-$$ signal.
- Contamination cannot be fully removed due to frequency-dependent CIB distribution.
- Current tSZ-$$ analyses are highly biased by CIB-$$ contamination.

## Abstract

The recent release of {\it Planck} data gives access to a full sky coverage of the thermal Sunyaev-Zel'dovich (tSZ) effect and of the cosmic microwave background (CMB) lensing potential ($\phi$). The cross-correlation of these two probes of the large-scale structures in the Universe is a powerful tool for testing cosmological models, especially in the context of the difference between galaxy clusters and CMB for the best-fitting cosmological parameters. However, the tSZ effect maps are highly contaminated by cosmic infra-red background (CIB) fluctuations. Unlike other astrophysical components, the spatial distribution of CIB varies with frequency. Thus it cannot be completely removed from a tSZ Compton parameter map, which is constructed from a linear combination of multiple frequency maps. We have estimated the contamination of the CIB-$\phi$ correlation in the tSZ-$\phi$ power-spectrum. We considered linear combinations that reconstruct the tSZ Compton parameter from {\it Planck} frequency maps. We conclude that even in an optimistic case, the CIB-$\phi$ contamination is significant with respect to the tSZ-$\phi$ signal itself. Consequently, We stress that tSZ-$\phi$ analyses that are based on Compton parameter maps are highly limited by the bias produced by CIB-$\phi$ contamination.