(Polarisation Angle Correcting rotation Measure ANalysis)


Pacerman is a new method to calculate Faraday rotation measure maps from multi-frequency polarisation angle data. In order to solve the so called n-pi-ambiguity problem which arises from the observationally ambiguity of the polarisation angle which is only determined up to additions of n times pi, where n is an integer, we suggest using a global scheme. Instead of solving the n-pi-ambiguity for each data point independently, our algorithm, which we chose to call Pacerman solves the n-pi-ambiguity for a high signal-to-noise region ``democratically'' and uses this information to assist computations in adjacent low signal-to-noise areas.


This software package is developed and brought to you by

Klaus Dolag (kdolag<at>

Corina Vogt (cvogt<at>

Torsten Ensslin (ensslin<at>

Copyrights and Acknowledgements

Download Sourcecode

Pacerman is written in the IDL language. To install it you have just to copy the files to a place, where your IDL enviroment automaticly finds the procedures. The fitting subroutine used in Pacerman requires IDL v5.4 or higher. To run it on your data, have a look into the file and replace the dummy placeholders giving the filenames, frequencies, etc. of your data. To start the analysis you just have to type pacerman on your IDL prompt and give as first parameter the dataset-identifier you defined when editing For all further options have a look into the file which holds a short explanation of all additional parameters. Please send your comments/suggestions to Klaus Dolag and please apologize, that so far we haven't found a way to program a user-friendly interface for common use.

As Pacerman reads and write fits files, so you need parts of the IDL Astronomy User's Library.


Example (HydraA)

We thank Greg Taylor for providing the data of HydraA for this demonstration.

From left to right: RM map obtained from Pacerman, RM map obtained using standard fitting method, Quality map obtained from Pacerman.

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