Open AccessThe optical polarization of spiral galaxies
Author(s) -
Simmons John F. L.,
Audit Edouard
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03863.x
Subject(s) - physics , starlight , spiral galaxy , astrophysics , rayleigh scattering , galaxy , polarization (electrochemistry) , scattering , circular symmetry , stars , classical mechanics , optics , chemistry
Scattering of starlight by dust, molecules and electrons in spiral galaxies will produce a modification of the direct intensity and a polarization in the observed light. We treat the case where the distribution of scatterers can be considered to be optically thin, and derive semi‐analytic expressions for the resolved intensity and polarized intensity for Thomson, Rayleigh, and more general scattering mechanisms. These expressions are applied to a parametric model for spiral galaxies. It is further shown that in the case of Thomson and Rayleigh scattering, and when scatterers and stars are distributed with rotational symmetry, the total polarized flux depends on the inclination, i , of the galactic axis to the line of sight according to a simple sin 2 i law. This generalizes the well‐known result for point‐like and spherical light sources. By using a method based on spherical harmonics, we generalize this law for more general mechanisms, and show that to good approximation, the sin 2 i law still holds for the class of models considered.