Evidence for cospatial optical and radio polarized emission in active galactic nuclei

Denise C. Gabuzda, Elizaveta A. Rastorgueva, Paul S. Smith, Shane P. O'Sullivan

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


We investigate the relationship between the optical and radio emission of active galactic nuclei (AGN) by analysing optical and 15+22+43 GHz Very Long Baseline Array (VLBA) polarization observations simultaneous to within a day for 11 BL Lacertae (BL Lac) objects and the blazar 3C279. We have determined and corrected for the Faraday rotation measures in the very long baseline interferometry (VLBI) cores, enabling us to compare the intrinsic (zero-wavelength) VLBI-core polarization angles and the optical polarization angles χopt. A clear alignment between these two angles emerges in the transition toward higher radio frequencies, and a prominent peak at 0° is visible in the distribution of |χopt - χ43GHz- This correlation implies that the magnetic-field orientations in the regions giving rise to the optical and radio polarization are the same, and can be easily understood if the radio and optical polarization are roughly cospatial. It is difficult to rule out the possibility that they arise in different regions in a straight jet with a uniform magnetic-field structure, but this seems less likely, since the VLBI jets of AGN are often bent on parsec-scales. This may suggest that much or all of the strong optical polarization in these sources arises in the inner radio jets, possibly associated with the formation and emergence of compact new VLBI components.

Original languageEnglish (US)
Pages (from-to)1596-1602
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jul 2006


  • Galaxies: active
  • Galaxies: fields
  • Galaxies: jets
  • Polarization

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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