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

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

The Astrophysical Journal, Volume 793, Issue 2, article id. 81, 7 pp. (2014).

Advertised on:
10
2014
Number of authors
13
IAC number of authors
3
Citations
13
Refereed citations
13
Description
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.
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