Dark Radiation after Planck

TL;DR

This paper analyzes Planck 2013 data to constrain dark radiation and lensing amplitude, finding evidence for dark radiation at over 91% confidence and a higher lensing amplitude, with comparisons to ACT and SPT results.

Contribution

It provides new constraints on N_eff and A_L using Planck data, highlighting potential dark radiation presence and lensing amplitude deviations.

Findings

N_eff = 3.71 +/- 0.40 at 68% c.l.

A_L = 1.25 +/- 0.13 at 68% c.l.

Suggests dark radiation at 91.1% confidence.

Abstract

We present new constraints on the relativistic neutrino effective number N_eff and on the Cosmic Microwave Background power spectrum lensing amplitude A_L from the recent Planck 2013 data release. Including observations of the CMB large angular scale polarization from the WMAP satellite, we obtain the bounds N_eff = 3.71 +/- 0.40 and A_L = 1.25 +/- 0.13 at 68% c.l.. The Planck dataset alone is therefore suggesting the presence of a dark radiation component at 91.1% c.l. and hinting for a higher power spectrum lensing amplitude at 94.3% c.l.. We discuss the agreement of these results with the previous constraints obtained from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT). Considering the constraints on the cosmological parameters, we found a very good agreement with the previous WMAP+SPT analysis but a tension with the WMAP+ACT results, with the only exception of the lensing amplitude.