The LOFAR View of Cosmic Magnetism

TL;DR

This paper discusses how LOFAR radio telescope observations at low frequencies are advancing the understanding of cosmic magnetic fields through polarization and Faraday rotation measurements, revealing structures in galaxies, clusters, and the Milky Way.

Contribution

It presents new low-frequency polarization observations with LOFAR, demonstrating the capability to map and analyze weak magnetic fields in various cosmic environments.

Findings

First images of magnetic structures in galaxies and clusters with LOFAR.

Detection of polarized emission from a magnetic bubble in the Milky Way.

Measurement of rotation measures for over 20 pulsars.

Abstract

The origin of magnetic fields in the Universe is an open problem in astrophysics and fundamental physics. Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of magnetic fields and should help to understand their origin. At low frequencies, LOFAR (10-240 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies, in galaxy clusters and in the Milky Way via their synchrotron emission. Even weaker magnetic fields can be measured at low frequencies with help of Faraday rotation measures. A detailed view of the magnetic fields in the local Milky Way will be derived by Faraday rotation measures from pulsars. First promising images with LOFAR have been obtained for the Crab pulsar-wind nebula, the spiral galaxy M51, the radio galaxy M87 and the galaxy clusters A2255 and A2256. With help of the polarimetric technique of "Rotation Measure Synthesis", diffuse polarized emission has been detected from a magnetic bubble in the local Milky Way. Polarized emission and rotation measures were measured for more than 20 pulsars so far.