6533b85efe1ef96bd12c06a3
RESEARCH PRODUCT
Measuring the cosmological background of relativistic with the Wilkinson Microwave Anisotropy Probe
Julien LesgourguesSergio PastorPatrick Crottysubject
PhysicsNuclear and High Energy PhysicsParticle physicsCosmic microwave backgroundFísicaAstrophysics::Cosmology and Extragalactic AstrophysicsLambdaCMB cold spotRelativistic particleBig Bang nucleosynthesisObservational cosmologyNeutrinoAnisotropydescription
We show that the first year results of the Wilkinson Microwave Anisotropy Probe (WMAP) constrain very efficiently the energy density in relativistic particles in the Universe. We derive new bounds on additional relativistic degrees of freedom expressed in terms of an excess in the effective number of light neutrinos $\ensuremath{\Delta}{N}_{\mathrm{eff}}.$ Within the flat \ensuremath{\Lambda}CDM scenario, the allowed range is $\ensuremath{\Delta}{N}_{\mathrm{eff}}l6$ (95% confidence level) using WMAP data only, or $\ensuremath{-}2.6l\ensuremath{\Delta}{N}_{\mathrm{eff}}l4$ with the prior ${H}_{0}=72\ifmmode\pm\else\textpm\fi{}8\mathrm{km}{\mathrm{s}}^{\ensuremath{-}1}{\mathrm{Mpc}}^{\ensuremath{-}1}.$ When other cosmic microwave background and large scale structure experiments are taken into account, the window shrinks to $\ensuremath{-}1.6l\ensuremath{\Delta}{N}_{\mathrm{eff}}l3.8.$ These results are in perfect agreement with the bounds from primordial nucleosynthesis. Nonminimal cosmological models with extra relativistic degrees of freedom are now severely restricted.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2003-06-24 |