Polarimetric studies on Interstellar grains

光谱和光谱偏振测量已经在银河系平面上对变红的巨星和超巨星、年轻的恒星物体暗云和暗云的背景恒星进行了测量。银河系平面上的红色恒星来自I波段物镜观测，其中大多数被证明是适度变红的M型恒星，本质上是红色的。它们的消光和偏振与文献中的关系非常吻合；这表明，即使在暗云中，颗粒产生消光和偏振的方式与扩散云中的相同。根据他们的观测，我们证明了其中一些天体在3.4微米处表现出深度吸收，并且3.4微米的吸收特征随着星际灭绝而增强。其中一个天体在3.0微米处的冰带中显示出偏振过剩。这个物体在研究冰的性质时将是一个有用的工具，因为它位于暗云的后面，没有散射效应。许多年轻恒星在暗云中的光谱偏振测量也是在冰带中进行的。用模型计算比较了取向效率，通常的磁场对取向是足够的。另一方面，吸收和偏振的光谱形状很难用实验室模拟的星际冰再现，在恒星形成区发现了许多具有冰带吸收和3.3微米发射特征的天体。其中一些需要更高空间分辨率的进一步观测。

Spectroscopy and spectro-polarimetry have been made for reddened giants and supergiants in the Galactic plane, young stellar objects dark clouds, and back ground stars of dark clouds. Reddened stars in the Galactic plane is from an I-band objective prism survey, and most of them have turned out to be moderately reddened M-type stars that are intrinsically red. Their extinction and polarization agree fairly well with the relationship in the literature ; this suggests that even in dark clouds grains produce extinction and polarization in the same manner as in diffuse clouds. From their observations, we demonstrate that some of them show deep absorption at 3.4 microns, and that the 3.4 micron absorption feature increases with the interstellar extinction.One objects show a polarization excess in the ice band at 3.0 microns. This objects would be a useful tool when studying the ice properties because it is located behind a dark cloud and free from scattering effect. Spectro-polarimetry of many young stellar objects in dark clouds are also made in the ice band. The grain alignment efficiency have been compared with a model calculation, and usual magnetic field seems to be sufficient for the alignment. On the other hand, the spectral shape of the absorption and polarization is difficult to be reproduced by laboratory analogs of the interstellar ice.A number of objects with the ice band absorption and the 3.3 micron emission feature have been found in star forming regions. Some of them require further observations of higher spatial resolution.