天文学进展Issue(2)：194-209,16.DOI:10.3969/j.issn.1000-8349.2014.02.05
大小麦哲伦云的星际消光
Interstellar Extinction in the Magellanic Clouds
摘要
Abstract
We review the extinction laws of the Magellanic Clouds (MCs) from the ultravi-olet (UV), optical to infrared and the 2D extinction maps of the MCs. The dust properties of the MCs are also discussed. The color excess E (B-V ) of the Large Magellanic Cloud (LMC) is about 0.13 mag. If RV=2.6 is adopted, the AV value is about 0.34 mag. The color excess E(B-V ) of the Small Magellanic Cloud (SMC) is about 0.16 mag, which corresponds to an AV of about 0.45 mag (for RV=2.8). The star formation regions LMC 30 Dor and Super Shell LMC 2 could be considered as relatively dense regions. They both lack the 2175˚A extinction bump feature and their extinction rises steeply in the UV range, while in the diffuse regions of LMC, the 2175˚A bump is relatively strong. As for the SMC, the 2175˚A bump is absent in the SMC bar region, and the extinction rises even more steeply in the UV band, while in the SMC wing region, the 2175˚A bump feature is present. In the infrared band, the ratio of the color excess E(J-H)/E(H-K) is roughly between 1.03 and 1.36 for LMC, clearly lower than the ratio of the Milky Way that is about 1.73. In SMC, the infrared extinction is fairly small, and as a tiny error of photometry or intrinsic color will bring large uncertainty, there is no consistent conclusion yet. The extinction curves of the LMC and SMC can not be described by the simple CCM parameterization containing a single param-eter RV which is valid for the Milky Way. By fitting the extinction curve as well as the infrared radiation of the Magellanic Clouds, it is found that the carbonaceous dust grains, compared to the silicate dust, are less abundant than those in the Milky Way. In particular, the lack of small carbonaceous dust grains is suggested to explain the weakness of the 2175˚A bump in the star-forming regions where the UV photons may destroy the very small carrier like graphite or PAH molecules. The dust-to-gas ratio in the MCs is significantly lower than that in the Milky Way very possibly due to the lower metallicity.关键词
星际消光/星际介质/麦哲伦云Key words
interstellar extinction/Magellanic clouds/ISM分类
天文与地球科学引用本文复制引用
薛梦瑶,姜碧沩,高健..大小麦哲伦云的星际消光[J].天文学进展,2014,(2):194-209,16.基金项目
973项目(2014CB845702)；国家自然科学基金(11373015,11173007) （2014CB845702）
