Polarized mid-infrared synchrotron emission in the core of Cygnus A
- Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States)
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)
- Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
- Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)
- Instituto de Física de Cantabria, CSIC-UC, E-39005 Cantabria (Spain)
- Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, E-38205 Tenerife (Spain)
- Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake cho, Kyoto 606-8502 (Japan)
- Gemini Observatory, Casilla 603, La Serena (Chile)
- Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain)
- Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900 (Brazil)
- Department of Astronomy, University of Florida, 211 Bryant Space Science Center, P.O. Box 11205, Gainesville, FL 32611-2055 (United States)
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.
- OSTI ID:
- 22370592
- Journal Information:
- Astrophysical Journal, Vol. 793, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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