Infrared polarimetry of Mrk 231: Scattering off hot dust grains in the central core

E. Lopez-Rodriguez, C. Packham, T. J. Jones, R. Siebenmorgen, P. F. Roche, N. A. Levenson, A. Alonso-Herrero, E. Perlman, K. Ichikawa, C. Ramos Almeida, O. González-Martín, R. Nikutta, M. Martinez-Paredez, D. Shenoy, M. S. Gordon, C. M. Telesco

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

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° ± 23° surrounding the central engine, and (3) an extinguished (AV = 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°) 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.

Original languageEnglish
Pages (from-to)1762-1770
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume464
Issue number2
DOIs
Publication statusPublished - 2017

Keywords

  • Galaxies: Seyfert
  • Galaxies: active
  • Infrared: galaxies
  • Techniques: high angular resolution
  • Techniques: polarimetric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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