Journal article
INTEGRATED POLARIZATION OF SOURCES AT lambda similar to 1 m AND NEW ROTATION MEASURE AMBIGUITIES
The Astronomical journal, Vol.141(6), 191
06/01/2011
DOI: 10.1088/0004-6256/141/6/191
Abstract
We present an analysis of the polarization of compact radio sources from six pointings of the Westerbork Synthesis Radio Telescope at 350 MHz with 35% coverage in lambda(2). After correcting for the off-axis instrumental polarization with a simple analytical model, only a small number of 585 strong sources have significant polarizations at these wavelengths. The median depolarization ratio from 1.4 GHz for the strongest sources is <0.2, reinforcing the likelihood that radio galaxies are found in magnetized environments, even outside of rich clusters. Seven sources with significant 350 MHz polarization were selected for a more in-depth Faraday structure analysis. We fit the observed values Q/I and U/I as a function of lambda(2) using both a depolarizing screen and two-component models. We also performed rotation measure (RM) Synthesis/Clean and standard fitting of polarization angle versus lambda(2). We find that a single RM, as found using polarization angle fitting or simple screen models, commonly provides a poor fit when the solutions are translated back into Q, U space. Thus, although a single "characteristic" RM may be found using these techniques, the Faraday structure of the source may not be adequately represented. We also demonstrate that RM Synthesis may yield an erroneous Faraday structure in the presence of multiple, interfering RM components, even when cleaning of the Faraday spectrum is performed. We briefly explore the conditions under which RMs and Faraday structure results can be reliable. Many measurements in the literature do not meet these criteria; we discuss how these influence the resulting scientific conclusions and offer a prescription for obtaining reliable RMs.
Details
- Title: Subtitle
- INTEGRATED POLARIZATION OF SOURCES AT lambda similar to 1 m AND NEW ROTATION MEASURE AMBIGUITIES
- Creators
- Damon Farnsworth - University of MinnesotaLawrence Rudnick - University of MinnesotaShea Brown - Australia Telescope National Facility
- Resource Type
- Journal article
- Publication Details
- The Astronomical journal, Vol.141(6), 191
- DOI
- 10.1088/0004-6256/141/6/191
- ISSN
- 0004-6256
- eISSN
- 1538-3881
- Publisher
- Iop Publishing Ltd
- Number of pages
- 28
- Grant note
- 0908668 / Division Of Astronomical Sciences; National Science Foundation (NSF); NSF - Directorate for Mathematical & Physical Sciences (MPS) National Aeronautics and Space Administration; National Aeronautics & Space Administration (NASA) AST 0908668 / U.S. National Science Foundation; National Science Foundation (NSF) Netherlands Foundation for Scientific Research (NWO); Netherlands Organization for Scientific Research (NWO)
- Language
- English
- Date published
- 06/01/2011
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428838202771
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