Polarized Mid-Infrared Synchrotron Emission in the Core of Cygnus A

Abstract

We present high-angular (~0.4") resolution mid-infrared (MIR) polarimetric observations in the 8.7 $\mu$m and 11.6 $\mu$m 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$\pm$3% and 12$\pm$3% and position angle of polarization of 27$\pm$8 degrees and 35$\pm$8 degrees 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 pc-scale jet close to the core of Cygnus A. Based on our polarization model, the synchrotron emission from the pc-scale jet is estimated to be 14% and 17% of the total flux density in the 8.7 $\mu$m and 11.6 $\mu$m 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.

8 pages, 2 figures (Accepted for publication in ApJ)

References in corpus (5)

• An Analysis of the Shapes of Interstellar Extinction Curves. VI. The Near-IR Extinction Law
• Gemini Imaging of Mid-IR Emission from the Nuclear Region of Centaurus A
• Gemini Mid-IR Polarimetry of NGC1068: Polarized Structures Around the Nucleus
• Subaru Spectroscopy and Spectral Modeling of Cygnus A
• Near-infrared Hubble Space Telescope polarimetry of a complete sample of narrow-line radio galaxies

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• Imaging the AGN Torus in Cygnus
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• eROSITA Final Equatorial-Depth Survey (eFEDS): eFEDS X-ray view of WERGS Radio Galaxies selected by the Subaru/HSC and VLA/FIRST survey
• Optical/infrared polarised emission in X-ray binaries
• Forgotten treasures in the HST/FOC UV imaging polarimetric archives of active galactic nuclei. IV. 5 Orphaned AGNs