Pacerman
(Polarisation Angle Correcting rotation Measure ANalysis)
Abstract
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.
Authors
This software package is developed and brought to you by
Klaus Dolag (kdolag<at>pd.astro.it)
Corina Vogt (cvogt<at>mpa-garching.mpg.de)
Torsten Ensslin (ensslin<at>mpa-garching.mpg.de)
Copyrights and Acknowledgements
- Pacerman is free software, distributed under the
GNU General Public License. This implies that you may freely distribute and copy the software. You may
also modify it as you wish, and distribute these modified versions as long as you indicate prominently any
changes you made in the original code, and as long as you leave the copyright notices, and the no-warranty
notice intact. Please read the General Public License for more details. Note that the authors retain their
copyright on the code.
- Requested Acknowledgement
The authors kindly ask you to acknowledge the use of the Pacerman package
in your publications in the following form:
- At the first use of the Pacerman acronym, a footnote placed in the main body of the paper
referring to the Pacerman web-site - currently http://www.mpa-garching.mpg.de/~kdolag/Pacerman
- A reference to Dolag, Vogt & Ensslin (2004,astro-ph/0401214)
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 get_dataset.pro 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 get_dataset.pro. For all further options have a look
into the pacerman.pro 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.
History
- 23.01.2004: First public version, v 1.0
- 07.03.2005: Minor bug fixes and renmamed to pacerman, v 1.1
- 20.07.2005: Minor bug fixes and improvements pacerman, v 1.2
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.
Related Publications
- Pacerman (I): A new algorithm to calculate RM maps
K. Dolag, C. Vogt, T. A. Ensslin, 2005,
(MNRAS, 358, 726
- Pacerman (II): Application and Testing
C. Vogt, K. Dolag, T. A. Ensslin, 2005,
MNRAS, 358, 732
- A Bayesian view on Faraday rotation maps Seeing the magnetic power spectra in galaxy clusters
C. Vogt, K. Dolag, T. A. Ensslin, 2005,
A & A, 434, 67
