CMB Neutrino Mass Bounds and Reionization

TL;DR

This paper explores how relaxing the reionization assumptions in CMB data analysis can significantly loosen the bounds on neutrino masses and improve consistency with observed small-scale structure signals.

Contribution

It introduces a principal component approach to model reionization more generally, revealing that neutrino mass bounds are less restrictive than previously thought.

Findings

Neutrino mass bounds can be relaxed by ~40% with generalized reionization.

The amplitude of matter fluctuations σ8 is lower, aligning better with SZ observations.

Reionization modeling impacts cosmological parameter constraints significantly.

Abstract

Current cosmic microwave background (CMB) bounds on the sum of the neutrino masses assume a sudden reionization scenario described by a single parameter that determines the onset of reionization. We investigate the bounds on the neutrino mass in a more general reionization scenario based on a principal component approach. We found the constraint on the sum of the neutrino masses from CMB data can be relaxed by a $\sim$40% in a generalized reionization scenario. Moreover, the amplitude of the r.m.s. mass fluctuations $\sigma_8$ is also considerably lower providing a better consistency with a low amplitude of the Sunyaev-Zel'dovich signal.