Project Part A1: Magnetic fields in the Milky Way
Persons involved
Summary
Cosmic magnetic fields are studied with the highest possible spatial resolution in Galactic objects, e.g. supernova remnants and HII regions, as well as in the diffuse Galactic interstellar medium. At low frequencies, steep-spectrum synchrotron sources and diffuse synchrotron emission clearly dominate the thermal emission. However, at low frequencies, thermal gas becomes optically thick, which implies absorption. This is a powerful tool to investigate the synchrotron emissivity distribution in the Milky Way. Rotation measures (RMs) depend on λ2, so that weak magnetic fields in low-density thermal gas can best be traced by low-frequency observations. High- resolution studies of polarised Galactic emission with LOFAR will reveal the properties of the magnetised Galactic interstellar medium on the smallest scales ever possible. It will constrain the properties of the turbulent Galactic magnetic field component and its coupling to the low-density warm gas.
Galactic polarised emission acts as a foreground for sensitive extragalactic polarisation observa- tions and must be separated. Investigations of the statistical properties of polarised emission or the distribution of RMs and modelling efforts are needed for a proper Galactic foreground separation.