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Planck 2015 results. XIX. Constraints on primordial magnetic fields

Abstract : We predict 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; 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 B1Mpc<4.4 nG (where B1Mpc is the comoving field amplitude at a scale of 1 Mpc) at 95% confidence level, assuming zero helicity, and B1Mpc<5.6 nG when we consider a maximally helical field. For nearly scale-invariant PMFs we obtain B1Mpc<2.1 nG and B1Mpc<0.7 nG if the impact of PMFs on the ionization history of the Universe is included in the analysis. 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 B1Mpc<2.8 nG. A search for preferred directions in the magnetically-induced passive bispectrum yields B1Mpc<4.5 nG, whereas the the compensated-scalar bispectrum gives B1Mpc<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 B1Mpc<1380 nG. In our final analysis, we consider the harmonic-space correlations produced by Alfv\'en 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.
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Submitted on : Tuesday, February 10, 2015 - 4:57:14 PM
Last modification on : Tuesday, October 19, 2021 - 11:06:45 AM

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P.A.R. Ade, Angélique Benoit, F. Couchot, S. Henrot-Versillé, A. Mangilli, et al.. Planck 2015 results. XIX. Constraints on primordial magnetic fields. Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 594, pp.A19. ⟨10.1051/0004-6361/201525821⟩. ⟨in2p3-01115270⟩



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