Complex Faraday depth structure of active galactic nuclei as revealed by broad-band radio polarimetry

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DOIResolve DOI: http://doi.org/10.1111/j.1365-2966.2012.20554.x
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TypeArticle
Journal titleMonthly Notices of the Royal Astronomical Society
ISSN0035-8711
Volume421
Issue4
Pages33003315; # of pages: 16
AbstractWe present a detailed study of the Faraday depth structure of four bright (>1 Jy), strongly polarized, unresolved radio-loud quasars. The Australia Telescope Compact Array (ATCA) was used to observe these sources with 2 GHz of instantaneous bandwidth from 1.1 to 3.1 GHz. This allowed us to spectrally resolve the polarization structure of spatially unresolved radio sources, and by fitting various Faraday rotation models to the data, we conclusively demonstrate that two of the sources cannot be described by a simple rotation measure (RM) component modified by depolarization from a foreground Faraday screen. Our results have important implications for using background extragalactic radio sources as probes of the Galactic and intergalactic magneto-ionic media as we show how RM estimations from narrow-bandwidth observations can give erroneous results in the presence of multiple interfering Faraday components. We postulate that the additional RM components arise from polarized structure in the compact inner regions of the radio source itself and not from polarized emission from galactic or intergalactic foreground regions. We further suggest that this may contribute significantly to any RM time variability seen in RM studies on these angular scales. Follow-up, high-sensitivity very long baseline interferometry (VLBI) observations of these sources will directly test our predictions. © 2012 CSIRO. Monthly Notices of the Royal Astronomical Society © 2012 RAS.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Herzberg Institute of Astrophysics (HIA-IHA)
Peer reviewedYes
NPARC number21269167
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Record identifier05e0b03f-5e88-4e8c-b5e8-4056127c69e6
Record created2013-12-12
Record modified2016-05-09
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