尘埃

• 消光曲线
• 发射线的消光可能和连续谱的消光不同
• Halpha/Hbeta 线比

内禀数值：2.86（恒星形成），3.1（AGN） 参见Osterbrock & Ferland 2006

• 尘埃在8000A左右有一个Extended Red Emission(ERE)的连续谱发射
• 尘埃的红外发射: dustEM
• 尘埃与气体有关，气体的光深可以从low-ionization interstellar (IS) absorption lines(e.g., Si II, O I, Fe II)获得 (Shapley et al. 2003)

e.g. If the two Si II transitions at 1260 and 1527A are optically thin, then the ratio of their equivalent widths will be W1260/W1527 > 6. The observed ratio is W1260/W1527 ~ 1, implying that the lines are saturated and hence their depths are sensitive to the covering fraction of Si II-enriched material.

对于比912A更短的波长来说，气体的吸收消光是最主要的而不是dust，但是气体和尘埃是相关的，参见[1]

• 盘星系的尘埃分布,Herschel的结果

可以延展到2R25，[2]:

密度轮廓比较follow恒星，而不是恒星形成（气体？）

有温度梯度，从中心25K到边缘15K

盘上的尘埃可以解释类星体的受到的intergalactic的红化现象？

• 模型THEMIS The Heterogeneous dust Evolution Model for Interstellar Solids) [3]
• 分子云中的turblence导致尘埃粒子按照颗粒大小分层分布[4] however we find evidence for 'size-sorting' of grains, where turbulence preferentially concentrates larger grains into dense regions. Size-sorting may help to explain observations of 'coreshine' from dark clouds, and why extinction laws differ along lines of sight through molecular clouds in the Milky Way compared to the diffuse interstellar medium.