Planck 2015 results. XIX. Constraints on primordial magnetic fields

P.A.R Ade, N. Aghanim, M. Arnaud, F. Arroja, M. Ashdown, J. Aumont, C. Baccigalupi, Rosa Maria Ballardini, A.J. Banday, R.B. Barreiro, N. Bartolo, Per Rex Christensen, Pavel Nasselski, Anne Mette Frejsel, Igor Dmitrievich Novikov, Hans Ulrik Nørgaard-Nielsen