Bibcode
Lopez-Rodriguez, E.; Packham, C.; Roche, P. F.; Alonso-Herrero, A.; Díaz-Santos, T.; Nikutta, R.; González-Martín, O.; Álvarez, C. A.; Esquej, P.; Rodríguez Espinosa, J. M.; Perlman, E.; Ramos Almeida, C.; Telesco, C. M.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 458, Issue 4, p.3851-3866
Advertised on:
6
2016
Citations
19
Refereed citations
17
Description
We present subarcsecond 7.5-13 μm imaging- and spectro-polarimetric
observations of NGC 1068 using CanariCam on the 10.4-m Gran Telescopio
CANARIAS. At all wavelengths, we find: (1) A 90 × 60 pc extended
polarized feature in the northern ionization cone, with a uniform
˜44° polarization angle. Its polarization arises from dust and
gas emission in the ionization cone, heated by the active nucleus and
jet, and further extinguished by aligned dust grains in the host galaxy.
The polarization spectrum of the jet-molecular cloud interaction at
˜24 pc from the core is highly polarized, and does not show a
silicate feature, suggesting that the dust grains are different from
those in the interstellar medium. (2) A southern polarized feature at
˜9.6 pc from the core. Its polarization arises from a dust
emission component extinguished by a large concentration of dust in the
galaxy disc. We cannot distinguish between dust emission from
magnetically aligned dust grains directly heated by the jet close to the
core, and aligned dust grains in the dusty obscuring material
surrounding the central engine. Silicate-like grains reproduce the
polarized dust emission in this feature, suggesting different dust
compositions in both ionization cones. (3) An upper limit of
polarization degree of 0.3 per cent in the core. Based on our
polarization model, the expected polarization of the obscuring dusty
material is ≲0.1 per cent in the 8-13 μm wavelength range. This
low polarization may be arising from the passage of radiation through
aligned dust grains in the shielded edges of the clumps.