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).
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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