Broad-band, radio spectro-polarimetric study of 100 radiative-mode and jet-mode AGN

S. P. O'Sullivan*, C. R. Purcell, C. S. Anderson, J. S. Farnes, X. H. Sun, B. M. Gaensler

*Corresponding author for this work

Research output: Contribution to journalArticle

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We present the results from a broad-band (1 to 3 GHz), spectro-polarimetry study of the integrated emission from 100 extragalactic radio sources with the Australia Telescope Compact Array, selected to be highly linearly polarized at 1.4 GHz. We use a general-purpose, polarization model-fitting procedure that describes the Faraday rotation measure (RM) and intrinsic polarization structure of up to three distinct polarized emission regions or 'RM components' of a source. Overall, 37 per cent/52 per cent/11 per cent of sources are best fitted by one/two/three RM components. However, these fractions are dependent on the signal-to-noise ratio (S/N) in polarization (more RM components more likely at higher S/N). In general, our analysis shows that sources with high integrated degrees of polarization at 1.4 GHz have low Faraday depolarization, are typically dominated by a single RM component, have a steep spectral index and have a high intrinsic degree of polarization. After classifying our sample into radiative-mode and jet-mode AGN, we find no significant difference between the Faraday rotation or Faraday depolarization properties of jet-mode and radiative-mode AGN. However, there is a statistically significant difference in the intrinsic degree of polarization between the two types, with the jet-mode sources having more intrinsically ordered magnetic field structures than the radiative-mode sources. We also find a preferred perpendicular orientation of the intrinsic magnetic field structure of jet-mode AGN with respect to the jet direction, while no clear preference is found for the radiative-mode sources.

Original languageEnglish
Pages (from-to)4034-4062
Number of pages29
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - Aug 2017


  • techniques: polarimetric
  • galaxies: active
  • galaxies: jet
  • galaxies: magnetic fields
  • radio continuum: galaxies

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