PACERMAN - I. A new algorithm to calculate Faraday rotation maps

Abstract

We propose a new method to calculate Faraday rotation measure maps from multifrequency polarization angle data. In order to solve the so-called nπ-ambiguity problem which arises from the observational ambiguity of the polarization 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 PACERMAN (Polarization Angle CorrEcting Rotation Measure ANalysis), solves the nπ-ambiguity for a high signal-to-noise region 'democratically' and uses this information to assist computations in adjacent low signal-to-noise areas. © 2005 RAS.