Using BBN in cosmological parameter extraction from CMB: a forecast for Planck

Abstract

Data from future high-precision Cosmic Microwave Background (CMB) measurements will be sensitive to the primordial Helium abundance $Y_p$. At the same time, this parameter can be predicted from Big Bang Nucleosynthesis (BBN) as a function of the baryon and radiation densities, as well as a neutrino chemical potential. We suggest to use this information to impose a self-consistent BBN prior on $Y_p$ and determine its impact on parameter inference from simulated Planck data. We find that this approach can significantly improve bounds on cosmological parameters compared to an analysis which treats $Y_p$ as a free parameter, if the neutrino chemical potential is taken to vanish. We demonstrate that fixing the Helium fraction to an arbitrary value can seriously bias parameter estimates. Under the assumption of degenerate BBN (i.e., letting the neutrino chemical potential $\xi$ vary), the BBN prior's constraining power is somewhat weakened, but nevertheless allows us to constrain $\xi$ with an accuracy that rivals bounds inferred from present data on light element abundances.

14 pages, 4 figures; v2: minor changes, matches published version

References in corpus (1)

• Observational bounds on the cosmic radiation density

Cited by in corpus (10)

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• Primordial Nucleosynthesis: from precision cosmology to fundamental physics
• Signatures of a hidden cosmic microwave background
• Relic density of neutrinos with primordial asymmetries
• Constraining massive neutrinos using cosmological 21 cm observations
• Probing the Effective Number of Neutrino Species with Cosmic Microwave Background
• Primordial Helium Abundance from CMB: a constraint from recent observations and a forecast
• WMAP 5-year constraints on lepton asymmetry and radiation energy density: Implications for Planck
• Constraints on neutrino masses from WMAP5 and BBN in the lepton asymmetric universe
• Constraining Light Gravitino Mass from Cosmic Microwave Background