Linear polarization of interstellar radio-frequency absorption lines and magnetic field direction

Abstract

view Abstract Citations (17) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Linear polarization of interstellar radio-frequency absorption lines and magnetic field direction Kylafis, N. D. Abstract It is predicted that interstellar radio-frequency absorption lines in the direction of H II regions, supernova remnants, and hot cores of molecular clouds are linearly polarized. The amount of linear polarization may be as large as several percent if the optical depth is moderate and the number of extrema of the velocity component along the line of sight through the absorbing medium is small. The polarization is caused by the linear dichroism of the interstellar medium, which in turn arises from the non-LTE population of the magnetic sublevels. Analytic expressions are presented for the amount of polarization expected in radio-frequency lines from absorbing material undergoing one-dimensional, two-dimensional axisymmetric, and three-dimensional isotropic collapse. A relation is given between the polarization vector and the magnetic field direction. This relation applies when the Zeeman splitting exceeds both the collisional frequency and the radiative transition rate. Publication: The Astrophysical Journal Pub Date: December 1983 DOI: 10.1086/161520 Bibcode: 1983ApJ...275..135K Keywords: Gravitational Collapse; Interstellar Extinction; Interstellar Magnetic Fields; Linear Polarization; Molecular Clouds; Radio Sources (Astronomy); Absorption Spectra; H Ii Regions; Radiative Transfer; Radio Spectra; Supernova Remnants; Zeeman Effect; Astrophysics full text sources ADS |