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

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.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11]
  1. Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States)
  2. Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)
  3. Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
  4. Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)
  5. Instituto de Física de Cantabria, CSIC-UC, E-39005 Cantabria (Spain)
  6. Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, E-38205 Tenerife (Spain)
  7. Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake cho, Kyoto 606-8502 (Japan)
  8. Gemini Observatory, Casilla 603, La Serena (Chile)
  9. Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain)
  10. Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900 (Brazil)
  11. Department of Astronomy, University of Florida, 211 Bryant Space Science Center, P.O. Box 11205, Gainesville, FL 32611-2055 (United States)
Publication Date:
OSTI Identifier:
22370592
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; FLUX DENSITY; GALAXIES; INTERMEDIATE INFRARED RADIATION; POLARIZATION; RESOLUTION; SYNCHROTRON RADIATION; SYNCHROTRONS; WAVELENGTHS