Faraday tomography of the Galactic ISM with the WSRT

Abstract

In this thesis I use the novel technique of Rotation Measure synthesis (RMS) to study the Galactic interstellar medium. With RMS we can study Faraday rotation and synchrotron emission along the line of sight. I apply RMS to 4 data sets that we obtained with the WSRT. With RMS we can separate the signal of a polarized extragalactic source from the signal from our own Milky Way. Depending on the viewing direction in the Milky Way, the rotation measures of extragalactic sources and diffuse emission (dis)agree. We supplement our observations with MHD simulations of the Galactic ISM, to better understand how we can interpret the observed features as structure in the Galactic ISM and the Galactic magnetic field. Finally, we combined our results with literature values on pulsars, extragalactic sources, and the diffuse emission. We found a way to calculate the electron-density weighted line-of-sight magnetic field strength from the RM and DM that we can either measure or model for these sources. With all this information we determined that the large-scale magnetic field in the second Galactic quadrant shows much more structure than what the currently best available model can predict.