| Description: | Radio continuum observations made with the WSRT (at 18 and 20 cm) have recently been used to study the polarisation of several nearby galaxies. This project has made use of the rotation measure technique that Brentjens & de Bruyn have developed to derive the magnetic fields: it is the first time that this has been done in such a systematic way for a large number of galaxies. The magnetic field traced by these observations gives extra insight into the structure and energetics of the interstellar medium of these galaxies.
One of the most striking objects in the sample is NGC 4569. The background image shows the optical appearance: a normal inclined spiral disk with a small companion (IC 3583) just to the north. The WSRT data reveal the presence of two large lobes of radio continuum emission, shown with yellow contours, extending up to 75,000 lightyears on both sides of the disk. The orientation of the magnetic fields in this system (corrected for Faraday rotation) is shown with the white lines. For the most part, the magnetic fields trace the shape of the radio lobes, while they also run along a bridge of polarised emission between NGC 4569 and IC 3583. The origin of this polarised bridge is quite possibly related to an interaction between the two galaxies. This rotation measure technique will be even more relevant for LOFAR and APERTIF. |
