Moritz Lietzow-Sinjen
Institute of Theoretical Physics and Astrophysics, Kiel University
Far-infrared multiwavelength polarimetry of HL Tau using SOFIA/HAWC+
M. Lietzow-Sinjen and S. Wolf
We present polarimetric observations of the prominent protoplanetary disk of HL Tauri in the SOFIA/HAWC+ bands A (53 μm), C (89 μm), D (155 μm), and E (216 μm). These observations provide the opportunity to trace the magnetic field of the disk which is assumed to play an important role during the evolution of the disk, in particular the formation of planets. Moreover, they provide complementary constraints for the disk and selected dust properties. While the orientation of the linear polarization is almost consistent in bands A, C, and D, it changes in band E, indicative for the wavelength-dependent interplay of different underlying polarization mechanisms. By applying the 3D Monte Carlo radiative transfer code POLARIS, we simulated the thermally reemitted, subsequently scattered and thus, polarized radiation of the circumstellar material. The results show that in bands A, C, and D, the polarization can be attributed to emission of aligned dust grains, while in band E, the polarization pattern matches that of self-scattering. In order to achieve the observed polarization degree in band E, a maximum grain size in the order of a few tens of micrometers is required. In conclusion, these far-infrared polarimetric observations do not only give unique insights into the magnetic field strength and structure, but also provide complementary constraints for the disk density structure and dust properties if compared to flux measurements alone.
