银道面红外消光律及其与星际介质的关系

This project will study the variation of the interstellar extinction law in the infrared and its relation with the interstellar medium in the Milky Way. Infrared extinction is essential to recover the infrared intrinsic brightness (thus the distance) and colors of the objects and also to understand the nature of interstellar dust, and becomes increasingly important with the fast development of infrared observations. There have been several works that suggest no universal extinction law in the infrared. Our investigation of the infrared extinction law based on the ISO and Spitzer space observations further found a possible correlation between the variation of the infrared extinction law and the structure of the spiral arms. In order to understand the infrared extinction and its variation in the Milky Way, this project aims: (1) to determine the infrared extinction law and its variation in various environments such as dense clouds, transluscent cloud and diffuse cloud; (2) to study the relation of the infrared extinction law with the interstellar medium, i.e. the gas represented by CO and the dust exhibited by the interstellar infrared radiation; (3) to explain the variation of the infrared extinction law and its relation with the interstellar medium and the spiral arms, and to constrain the model of interstellar dust grains by the derived infrared extinction laws. Upon completion, this project will provide a convenient tool to correct for the infrared extinction in the Milky Way, and reveal the large-scale structure of the spatial distribution of the infrared extinction and the interstellar dust.

本项目旨在利用美国NASA 的Spitzer 空间望远镜保留项目GLIPMSE 和MIPSGAL 的数据，对银道面的红外星际消光律（消光随波长的变化）及其与星际介质之间的关系进行系统的研究。红外消光的研究非常重要，既是复原所观测天体的本征亮度（及距离）和颜色所必不可少的，也是了解星际尘埃的主要途径。研究表明银河系不存在普适的红外消光律，而且，有迹象表明消光律的变化与银经和银河系旋臂结构之间存在系统的相关性。本项目将（1）确定致密星云、弥漫星云等各种典型星际环境下的红外消光律及其变化规律，（2）研究消光律的变化与CO 分子以及尘埃的红外发射的空间分布之间的相关性，（3）探讨消光律随环境改变的原因，从而增进对星际尘埃物理、化学性质的了解。本项目的完成将为天文学家提供方便实用的红外消光改正工具，并且对了解银盘星际介质的大尺度结构和星际尘埃的性质具有重要意义。

摘要: （1）构建一种新的精确确定消光规律的方法，即：根据大量光谱巡天获得的恒星参数，得到内禀色指数与恒星参数（主要是有效温度）之间的关系，进而根据恒星参数计算单颗恒星的内禀色指数和色余，同时，基于大量恒星的数据，通过色余之间的线性拟合获得以色余之比表示的消光规律；（2）使用此种新方法，对近红外的消光规律进行了分析，得到近红外色余比E(J-H)/E(J-Ks)=0.652，而且，近红外的色余之比没有表现出对环境的依赖性，是普适的规律；（3）使用此种新方法，对中红外（3-24微米）波段的消光规律进行了分析，得到高精度的中红外10个波段（Spitzer/IRAC1-4，WISE/W1-W4，AKARI/S9W和Spitzer/MIPS24）与近红外Ks波段的相对消光值，为正确改正中红外的消光提供了基础，而且，中红外的消光也没有表现出明显的随消光大小而改变的趋势；（4）对现有的机遇可见光和紫外波段构建的星际尘埃模型进行了修改，通过增加微米尺寸的大尘埃颗粒，能够很好地解释我们得到的红外波段消光曲线的平坦性。