“奇异”(anomalous)星际消光、星际弥散带(DIBs)和多环芳香烃(PAHs)相关性研究

Dust extinction is a combination of scattering and absorption. The wavelength- dependence of the interstellar extinction, known as the interstellar extinction curve, contains useful information about dust composition and size distributions. While most of the extinction curves in the Milky Way galaxy can be closely fitted in terms of the Cardelli, Clayton and Mathis (1989; CCM) analytical formula, there are some sightlines toward which the extinction curves deviate substantially from the CCM formulae. These extinction curves are referred as anomalous extinction. We propose to study the interstellar extinction, particularly the 2175Å extinction bump and the far ultraviolet (UV) extinction rise of sightlines which exhibit an “anomalous” extinction curve. We will also study the diffuse interstellar bands (DIBs) of these sightlines and perform correlation studies between the 2175Å bump and the far-UV extinction with DIBs. We will model the observed 2175Å bump with a mixture of PAHs of various sizes and charge states (cation, neutral, anion) and then compare the optical/UV absorption spectra of the PAH mixtures with the observed DIBs.

星际消光随波长的变化取决于尘埃的组份、尺寸及形状。其研究,对于揭示星际介质的化学组成、了解星际物理、化学环境具有重要意义。星际弥散带(DIBs)是一系列叠加在星际消光曲线上的吸收带，自发现以来，其载体尚未获得证认。本项目重点研究具有奇异消光曲线的天体。我们将研究其消光曲线与DIBs及PAHs的紫外波段电子跃迁吸收谱的关系: (1) 广泛收集具有奇异消光曲线的天体之可见光、紫外消光观测数据, 定量分析可见光、2175Å驼峰、远紫外三部分消光的积分总量; (2) 观测、收集这些天体的DIBs, 研究这些天的DIBs与2175Å消光、远紫外消光参量之间的相关性; (3) 采用由实验测量或理论计算获得的PAHs π-π*电子吸收谱拟合各天体的2175Å消光驼峰，把这些PAHs的近紫外、可见光电子跃迁吸收谱与这些天体DIBs比较,从而对何种PAH有可能是哪一条或哪几条DIBs的载体作出限制。

星际消光随波长的变化取决于尘埃的组份、尺寸及形状。其研究,对于揭示星际介质的化学组成、了解星际物理、化学环境具有重要意义。星际弥散带(DIBs)是一系列叠加在星际消光曲线上的吸收带，自发现以来，其载体尚未获得证认。我们研究了奇异消光曲线与DIBs及PAHs的紫外波段电子跃迁吸收谱的关系: (1) 广泛收集了具有奇异消光曲线的天体之可见光、紫外消光观测数据, 定量分析了可见光、2175Å驼峰、远紫外三部分消光的积分总量; (2) 观测、收集了这些天体的DIBs, 研究了这些天的DIBs与2175Å消光、远紫外消光参量之间的相关性; (3)分析了PAHs的近紫外、可见光电子跃迁吸收谱,与这些天体DIBs进行了比较,寻找了它们之间的关系。