Delayed recombination and cosmic parameters

Abstract

Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, ${n}_{s}$, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to ${z}_{*}=1078\ifmmode\pm\else\textpm\fi{}11$, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by $1\ensuremath{\sigma}$ to $\mathcal{R}=1.734\ifmmode\pm\else\textpm\fi{}0.028$. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: ${ϵ}_{\ensuremath{\alpha}}<0.39$ and ${ϵ}_{i}<0.058$ at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.