Scattering and Dichroic Extinction: Polarimetric Signatures of Galaxies
Scattering and Dichroic Extinction: Polarimetric Signatures of Galaxies
复制标题
散射和二向色消光：星系的偏振特征
DOI：
10.1086/310518
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
K. Wood
中科院分区：
文献类型：
--
作者：
K. Wood
提出了星系偏振结构的辐射传输模型。这些模型包括尘埃散射和二向色消光（这种机制被认为是在我们自己的银河系中产生观测到的星际偏振的原因）。与以前的努力模拟银河系偏振图，散射模型产生的偏振矢量的中心对称图案，当一个人正在观看一个星系极上和矢量垂直于银河系平面的高度倾斜的星系。一般来说，星系的偏振观测显示出平行于银道面或遵循旋臂结构的矢量，这表明主要的偏振机制是来自光通过排列的颗粒的传输（二向色消光）。当我们在辐射传输模拟中包括一个环形磁场来排列尘埃颗粒和由此产生的二向色偏振时，我们确实发现偏振平行于星系盘。根据星系的光学深度和尘埃的性质（偏振度，相位函数，峰值散射偏振），在不同的区域内的星系的偏振模式显示的签名的二向色性，散射，和零点由于两个偏振机制之间的抵消。我们发现，为了再现外部星系的偏振结构，它是必不可少的，包括二向色消光的辐射传输。
Radiation transfer models of the polarization structure of galaxies are presented. These models include dust scattering and dichroic extinction (the mechanism believed to be responsible for producing the observed interstellar polarization within our own Galaxy). As with previous efforts to model galactic polarization maps, the scattering-only models produce a centrosymmetric pattern of the polarization vectors when one is viewing a galaxy pole-on and vectors perpendicular to the galactic plane for highly inclined galaxies. In general, polarization observations of galaxies show vectors that are parallel to the galactic plane or that follow the spiral arm structure, which indicates that the dominant polarization mechanism is from the transmission of light through aligned grains (dichroic extinction). When we include a toroidal magnetic field to align the dust grains and the resulting dichroic polarization in our radiation transfer simulations, we do indeed find that the polarization is parallel to the galactic disk. Depending on the optical depth of the galaxy and the dust properties (albedo, phase function, peak scattering polarization), the polarization patterns at different regions within the galaxy show the signatures of dichroism, scattering, and null points owing to cancellation between the two polarizing mechanisms. We find that in order to reproduce the polarization structure of external galaxies, it is essential to include dichroic extinction in the radiation transfer.