Pacman (I): A new algorithm to calculate Faraday Rotation maps

We propose a new method to calculate Faraday rotation measure maps from multi-frequency polarisation angle data. In order to solve the so called nπ-ambiguity problem which arises from the observationally ambiguity of the polarisation angle which is only determined up to additions of ±nπ, where n is an integer, we suggest using a global scheme. Instead of solving the nπ-ambiguity for each data point independently, our algorithm, which we chose to call Pacman (Polarisation Angle Correcting rotation Measure ANalysis), solves the nπambiguity for a high signal-to-noise region “democratically” and uses this information to assist computations in adjacent low signal-to-noise areas.