Polarized mid-infrared synchrotron emission in the core of Cygnus A

E. Lopez-Rodriguez, C. Packham, C. Tadhunter, R. Mason, E. Perlman, A. Alonso-Herrero, C. Ramos Almeida, K. Ichikawa, N. A. Levenson, J. M. Rodríguez-Espinosa, C. A. Álvarez, E. A. Ramírez, C. M. Telesco

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We present high-angular (∼0.″4) resolution mid-infrared (MIR) polarimetric observations in the 8.7 μm and 11.6 μm filters of Cygnus A using CanariCam on the 10.4 m Gran Telescopio CANARIAS. A highly polarized nucleus is observed with a degree of polarization of 11% ± 3% and 12% ± 3% and a position angle of polarization of 27° ± 8°and 35°± 8°in a 0.″38 (∼380 pc) aperture for each filter. The observed rising of the polarized flux density with increasing wavelength is consistent with synchrotron radiation from the parsec-scale jet close to the core of Cygnus A. Based on our polarization model, the synchrotron emission from the parsec-scale jet is estimated to be 14% and 17% of the total flux density in the 8.7 μm and 11.6 μm filters, respectively. A blackbody component with a characteristic temperature of 220 K accounts for >75% of the observed MIR total flux density. The blackbody emission arises from a combination of (1) dust emission in the torus; and (2) diffuse dust emission around the nuclear region, but the contributions of the two components cannot be well-constrained in these observations.

Original languageEnglish
Article number81
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2014 Oct 1


  • galaxies: active
  • galaxies: individual (Cygnus A)
  • infrared: galaxies
  • techniques: polarimetric


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