Infrared polarimetry of Mrk 231: scattering off hot dust grains in the central core. Issue 2 (30th September 2016)

• Record Type: Journal Article
• Authors: Lopez-Rodriguez, E.; Packham, C.; Jones, T. J.; Siebenmorgen, R.; Roche, P. F.; Levenson, N. A.; Alonso-Herrero, A.; Perlman, E.; Ichikawa, K.; Ramos Almeida, C.; González-Martín, O.; Nikutta, R.; Martinez-Paredez, M.; Shenoy, D.; Gordon, M. S.; Telesco, C. M.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 464:Issue 2(2017)
• Page Start: 1762
• Page End: 1770
• Publication Date: 2016-09-30
• Subjects: techniques: high angular resolution -- techniques: polarimetric -- galaxies: active -- galaxies: Seyfert -- infrared: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stw2491
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We present high-angular (0.17–0.35 arcsec) resolution imaging polarimetric observations of Mrk 231 in the 3.1 μm filter using MMT-Pol on the 6.5-m MMT, and in the 8.7, 10.3, and 11.6 μm filters using CanariCam on the 10.4-m Gran Telescopio CANARIAS. In combination with already published observations, we compile the 1–12 μm total and polarized nuclear spectral energy distribution (SED). The total flux SED in the central 400 pc is explained as the combination of (1) a hot (731 ± 4 K) dusty structure, directly irradiated by the central engine, which is at 1.6 ± 0.1 pc away and attributed to be in the pc-scale polar region, (2) an optically-thick, smooth and disc-like dusty structure ('torus') with an inclination of 48$^\circ$ ± 23$^\circ$ surrounding the central engine, and (3) an extinguished ( A V = 36 ± 5 mag) starburst component. The polarized SED decreases from 0.77 ± 0.14 per cent at 1.2 μm to 0.31 ± 0.15 per cent at 11.6 μm and follows a power-law function, λ ∼0.57 . The polarization angle remains constant (∼108$^\circ$ ) in the 1–12 μm wavelength range. The dominant polarization mechanism is explained as scattering-off hot dust grains in the pc-scale polar regions.