Robust Intensity Mapping Analysis against Foregrounds for the Epoch of Reionization

TL;DR

This paper introduces a novel method for analyzing intensity maps of the early universe's reionization epoch, effectively separating the cosmological signal from foreground contamination without traditional mitigation techniques.

Contribution

It proposes a new antisymmetric cross-correlation technique that is unbiased by foregrounds and can determine the reionization process's nature independently.

Findings

The antisymmetric HI-CO cross-correlation signal can be measured without foreground mitigation.

The sign of this signal indicates whether inside-out reionization occurs.

The method distinguishes reionization models in a model-independent manner.

Abstract

Intensity mapping of the HI 21 cm line and the CO 2.61 mm line from the epoch of reionization has emerged as powerful, complementary, probes of the high-redshift Universe. However, both maps and their cross-correlation are dominated by foregrounds. We propose a new analysis by which the signal is unbiased by foregrounds, i.e. it can be measured without foreground mitigation. We construct the antisymmetric part of the HI-CO cross-correlation, arising because the statistical fluctuations of two fields have different evolution in time. We show that the sign of this new signal can distinguish model-independently whether inside-out reionization happens during some interval of time.