Reionization optical depth determination from Planck HFI data with ten percent accuracy

TL;DR

This paper improves the measurement of the reionization optical depth using Planck HFI data, achieving a 10% accuracy, which significantly refines our understanding of the epoch of reionization.

Contribution

An improved analysis and map-making method reduces systematic contamination, leading to the most precise measurement of reionization optical depth to date.

Findings

Reionization optical depth measured as τ=0.0566 with reduced uncertainty.

Achieved 10% accuracy in estimating τ, the strongest constraint to date.

Refined the reionization redshift to z_re=8.14±0.61.

Abstract

We present an estimation of the reionization optical depth $\tau$ from an improved analysis of the High Frequency Instrument (HFI) data of Planck satellite. By using an improved version of the HFI map-making code, we greatly reduce the residual large scale contamination affecting the data, characterized, but not fully removed, in the Planck 2018 legacy release. This brings the dipole distortion systematic effect, contaminating the very low multipoles, below the noise level. On large scale polarization only data, we measure $\tau=0.0566_{-0.0062}^{+0.0053}$ at $68\%$ C.L., reducing the Planck 2018 legacy release uncertainty by $\sim40\%$. Within the $\Lambda$CDM model, in combination with the Planck large scale temperature likelihood, and the high-$\ell$ temperature and polarization likelihood, we measure $\tau=0.059\pm0.006$ at $68\%$ C.L. which corresponds to a mid-point reionization redshift of $z_{\rm re}=8.14\pm0.61$ at $68\%$ C.L.. This estimation of the reionization optical depth with $10\%$ accuracy is the strongest constraint to date.