Dynamical effects of the neutrino gravitational clustering at Planck angular scales

We study the CMB anisotropy induced by the non-linear perturbations in the massive neutrino density associated to the non-linear gravitational clustering process. By using N-body simulations, we compute the imprint left by the grav-itational clustering on the CMB anisotropy power spectrum for all non-linear scales taking into account the time evolution of all non-linear density perturbations , for a flat ΛCHDM model consistent with LSS data and latest CMB measurements for different neutrino fractions f ν corresponding to a neutrino total mass in the range allowed by the neutrino oscillation and double beta decay experiments. We find that the non-linear time varying potential induced by the gravita-tional clustering process generates metric perturbations, leaving a decrease in the CMB anisotropy power spectrum of amplitude ∆T /T ≈ 10 −6 for angular resolutions between ∼ 4 and 20 arcminutes, depending on the cluster mass scale and the neutrino fraction f ν. We find also that the consistency among BOOMERANG, MAXIMA-1 and DASI CMB angular power spectra and the errors on most of the cosmological parameters improve when the non-linear effects induced by the gravitational clustering are taken into account. Our results show that, for a neutrino fraction in agreement with that indicated by the astroparticle and nuclear physics experiments and a cosmological accreting mass comparable with the mass of known clusters, the angular resolution and sensitivity of the CMB anisotropy measurements from the Planck satellite will allow the detection of the dynamical effects of the gravitational clustering. This work has been done in the framework of the Planck LFI activities. Subject headings: Cosmology: cosmic microwave background – large scale – 3 – structure – dark matter – Elementary particles