标题： 远红外特征在恒星形成区域的检测 显示英文标题

标题： Detection of Far-Infrared Features in Star-Forming Regions

摘要： 我们报告在两个活跃恒星形成区域的弥漫辐射的远红外光谱中检测到65微米的特征以及约100微米的宽广特征，这两个区域分别是船底座星云和Sharpless 171。 这些特征在观测区域的广阔区域内可见，表明载体是星际介质中相当普遍的物质。 类似65微米的特征已在演化恒星中被检测到，并归因于透辉石，一种含钙的结晶硅酸盐。 如果这一识别也适用于星际特征，则目前的观测表明首次在星际介质中检测到结晶硅酸盐。 在演化恒星的光谱中曾报道过一个约90微米的宽广特征，并归因于方解石，一种含钙的碳酸盐矿物。 尽管对特征轮廓的精确估计较为困难，但星际特征似乎向更长波长移动且具有更宽的宽度。 作为星际100微米特征的载体，我们研究了该特征可能起源于碳洋葱，即由弯曲石墨壳层组成的颗粒。 由于弯曲石墨片结构，碳洋葱颗粒中平行于石墨平面方向的光学性质与垂直方向的光学性质相互作用。 这种效应增强了碳洋葱中平行于石墨平面方向的带间跃迁特征，而在石墨颗粒中该特征则被抑制。 简单的计算表明碳洋葱颗粒可能是观测到的100微米特征的可能载体，但该特征的表现对所假设的光学性质非常敏感。 显示英文摘要

摘要： We report the detection of a feature at 65um and a broad feature around 100um in the far-infrared spectra of the diffuse emission from two active star-forming regions, the Carina nebula and Sharpless 171. The features are seen in the spectra over a wide area of the observed regions, indicating that the carriers are fairly ubiquitous species in the interstellar medium. A similar 65um feature has been detected in evolved stars and attributed to diopside, a Ca-bearing crystalline silicate. The present observations indicate the first detection of a crystalline silicate in the interstellar medium if this identification holds true also for the interstellar feature. A similar broad feature around 90um reported in the spectra of evolved stars has been attributed to calcite, a Ca-bearing carbonate mineral. The interstellar feature seems to be shifted to longer wavelengths and have a broader width although the precise estimate of the feature profile is difficult. As a carrier for the interstellar 100um feature, we investigate the possibility that the feature originates from carbon onions, grains consisting of curved graphitic shells. Because of the curved graphitic sheet structure, the optical properties in the direction parallel to the graphitic plane interacts with those in the vertical direction in carbon onion grains. This effect enhances the interband transition feature in the direction parallel to the graphitic plane in carbon onions, which is suppressed in graphite particles. Simple calculations suggest that carbon onion grains are a likely candidate for the observed 100um feature carrier, but the appearance of the feature is sensitive to the assumed optical properties.