A Search for X-Ray Reionization Signatures from Cross-Correlation of Wmap and ROSAT Rass Data

TL;DR

This study searches for correlations between CMB polarization and soft X-ray background data to understand X-ray heating's role during reionization, but finds no significant correlation due to weak signals and noise.

Contribution

First observational attempt to cross-correlate CMB polarization with soft X-ray background data to probe reionization processes.

Findings

No significant correlation detected between CMB polarization and SXRB.

Results constrain the impact of X-ray heating during reionization.

Highlights need for higher sensitivity instruments in future studies.

Abstract

We present an observational search for the possible correlation between cosmic microwave background (CMB) polarization map and soft X-ray background (SXRB) based on the ROSAT All-sky Survey (RASS) archive and WMAP five-year observations. This is motivated by the fact that some of the CMB polarization may arise from the scattering of CMB photons due to the free electrons generated by X-ray heating sources in the epoch of reionization. Detection of such a correlation allows one to study the role of X-ray heating in the process of reionization. However, the cross angular power spectrum of the CMB polarization and SXRB maps constructed from ROSAT RASS and WMAP five-year maps is consistent with no correlation. We attribute this negative detection to both the extremely weak signals and large instrumental noises. While a future search is needed with high sensitivity instruments for both CMB polarization and soft X-ray photons, our current results can still be used as a useful constraint on the effect of X-ray heating in the epoch of reionization.