Polarimetric studies on Interstellar grains

光谱学和光谱偏振法已经对银河系平面上的红巨星和超巨星、年轻的恒星物体、黑云和黑云的背景恒星进行了研究。银河平面上的变红恒星来自于i波段物镜调查，其中大多数被证明是适度变红的m型恒星，它们本质上是红色的。它们的消失和极化与文献中的关系相当吻合；这表明，即使在乌云中，颗粒也会以与漫射云相同的方式产生消光和极化。从他们的观测中，我们证明了其中一些在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消光而增加。一个物体在3.0微米的冰带显示出偏振过剩。这个物体在研究冰的性质时将是一个有用的工具，因为它位于乌云的后面，没有散射效应。对黑云中许多年轻恒星的光谱偏振测量也在冰带中进行。并与模型计算结果进行了比较，结果表明，通常的磁场足以满足晶粒的取向。另一方面，吸收和极化的光谱形状很难被星际冰的实验室模拟物再现。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.