Cross-correlation analysis of CMB with foregrounds for residuals

TL;DR

This study assesses the presence of residual foreground contamination in cleaned CMB maps using cross-correlation, aiming to improve foreground masking and ensure the purity of cosmological signals.

Contribution

It introduces a method to detect residual foregrounds outside standard masks, enhancing the accuracy of CMB data analysis.

Findings

Identification of residual foreground regions outside masks

Potential to refine masks for cleaner CMB maps

Insights into foreground contamination distribution

Abstract

In this paper, we try to probe whether a clean CMB map obtained from the raw satellite data using a cleaning procedure is sufficiently clean. Specifically we study if there are any foreground residuals still present in the cleaned data using a cross-correlation statistic. Residual contamination is expected to be present, primarily, in the galactic plane due to the high emission from our own galaxy. A foreground mask is applied conventionally to avoid biases in the estimated quantities of interest due to foreground leakage. Here, we map foreground residuals, if present, in the unmasked region i.e., outside a CMB analysis mask. Further locally extended foreground-contaminated regions, found eventually, are studied to understand them better. The few contaminated regions thus identified may be used to slightly extend the available masks to make them more stringent.