2015/02/28 by Planck Collaboration, P. A. R. Ade, N. Aghanim +230 · 1 citation
Physics and Astronomy · #astro-ph.CO
paper · pdf · doi:10.1051/0004-6361/201525821
29 pages, 15 figures. Revised following referee report
arxiv created 2016/02/18 · arxiv updated 2016/09/28
We compute and investigate four types of imprint of a stochastic background of primordial magnetic fields (PMFs) on the cosmic microwave background (CMB) anisotropies: the impact of PMFs on the CMB spectra; the effect on CMB polarization induced by Faraday rotation; the impact of PMFs on the ionization history; magnetically-induced non-Gaussianities; and the magnetically-induced breaking of statistical isotropy. Overall, Planck data constrain the amplitude of PMFs to less than a few nanogauss. In particular, individual limits coming from the analysis of the CMB angular power spectra, using the Planck likelihood, are B1 Mpc< 4.4 nG (where B1 Mpc is the comoving field amplitude at a scale of 1 Mpc) at 95% confidence level, assuming zero helicity, and B1 Mpc< 5.6 nG for a maximally helical field.For nearly scale-invariant PMFs we obtain B1 Mpc<2.0 nG and B1 Mpc<0.9 nG if the impact of PMFs on the ionization history of the Universe is included. From the analysis of magnetically-induced non-Gaussianity we obtain three different values, corresponding to three applied methods, all below 5 nG. The constraint from the magnetically-induced passive-tensor bispectrum is B1 Mpc< 2.8 nG. A search for preferred directions in the magnetically-induced passive bispectrum yields B1 Mpc< 4.5 nG, whereas the the compensated-scalar bispectrum gives B1 Mpc< 3 nG. The analysis of the Faraday rotation of CMB polarization by PMFs uses the Planck power spectra in EE and BB at 70 GHz and gives B1 Mpc< 1380 nG. In our final analysis, we consider the harmonic-space correlations produced by Alfvén waves, finding no significant evidence for the presence of these waves. Together, these results comprise a comprehensive set of constraints on possible PMFs with Planck data.