星际碳化硅SiC尘埃

Interstellar SiC grains

碳化硅(SiC)尘粒是宇宙尘埃的重要成分之一,亚微米尺寸的SiC颗粒在11.3μm波长附近有非常显著的晶格振动带.早在20世纪60年代,Friedemann等人就预言了SiC尘粒可以冷凝在富碳恒星的质量流失喷出物中.随后,通过11.3μm的光谱特征,在碳星的星周包层检测到了SiC尘埃.另外,通过原始陨石中同位素异常发现前太阳(Presolar)SiC尘粒最终确立了SiC在星际介质中的存在.然而,令人困惑的是,在星际空间中并未观测到SiC的11.3μm吸收特征.本文主要介绍SiC的光学性质、SiC在天体环境中的观测特征,从而推断SiC在星际空间的丰度上限,并对其在星际空间中的演化进行理论分析.

Silicon carbide （SIC） is one of the major components of cosmic dust. Small silicon carbide dust particles show a prominent lattice vibrational band at -11.3 μm. In the 1960s, Friedemann et al. （1969） first predicted that SiC condenses in carbon-rich stellar ejecta. Later, SiC was detected in the circumstellar envelopes around evolved C stars through the 11.3 μm spectral feature. The existence of SiC in the interstellar medium （ISM） was established through the detection of presolar SiC grains in primitive meteorites based on the isotopic anomaly. However, the 11.3 μm absorption feature of SiC is surprisingly not seen in the ISM. This work mainly introduces the optical properties of silicon carbide, the observed characteristics of silicon carbon in a series of astrophysical environment, and abundance of silicon carbide in interstellar space and the underlying physics.