Polarized thermal emission from dust in a galaxy at redshift 2.6
J. E. Geach, Enrique López-Rodríguez, M. Doherty, Jianhang Chen, R. J. Ivison, G. J. Bendo, S. Dye, K. E. K. Coppin
Abstract
Abstract Magnetic fields are fundamental to the evolution of galaxies, playing a key role in the astrophysics of the interstellar medium and star formation. Large-scale ordered magnetic fields have been mapped in the Milky Way and nearby galaxies 1,2 , but it is not known how early in the Universe such structures formed 3 . Here we report the detection of linearly polarized thermal emission from dust grains in a strongly lensed, intrinsically luminous galaxy that is forming stars at a rate more than 1,000 times that of the Milky Way at redshift 2.6, within 2.5 Gyr of the Big Bang 4,5 . The polarized emission arises from the alignment of dust grains with the local magnetic field 6,7 . The median polarization fraction is of the order of 1%, similar to nearby spiral galaxies 8 . Our observations support the presence of a 5-kiloparsec-scale ordered magnetic field with a strength of around 500 μG or lower, oriented parallel to the molecular gas disk. This confirms that such structures can be rapidly formed in galaxies, early in cosmic history.