Speaker
Description
Polarisation studies over a significant redshift range are an important tool for understanding the evolution of cosmic magnetic fields and unrevealing their origin. As most depolarisation effects are highly wavelength dependent, the combination of different surveys allows us to distinguish between different effects.
We use the synergy of LOFAR and Apertif; starting with sources known to show significant polarised emission at 144 MHz, we image their 1.4 GHz counterparts and construct a catalogue of 598 polarised sources.
The comparison of polarisation properties, such as the fractional polarisation and the Rotation Measure values, at 1.4 GHz and 144 MHz provides us with information about the local environment of the sources as well as about the magnetic fields along the line of sight.
Combined with redshift information, we use this to study the evolution of the direct source environment and also to obtain a first redshift-dependent estimate of the Rotation Measure dispersion in cosmic web filaments.
We find a small fraction of sources to be more polarised at 144 MHz than at 1.4 GHz and two sources that don’t show significant polarisation in the Apertif data at all. We also present further investigation of those sources.
