风中尘埃：PG 2112+059中的结晶硅酸盐、硅酸盐和方镁石
Dust in the wind: Crystalline silicates, corundum and periclase in PG 2112+059
摘要：
利用斯皮策空间望远镜获得的中红外光谱，我们测定了宽吸收线（BAL）类星体PG 2112+059中尘埃的矿物组成。从光谱拟合的固态特征，我们发现的证据，富镁的无定形硅酸盐与橄榄石的化学计量比，以及第一次检测到的Al_2O_3和方镁石（MgO）的类星体。这种混合成分为颗粒形成区的块状密度结构提供了第一个直接证据。硅酸盐总共占已识别粉尘质量的56.5%，而硅酸盐占38重量%。根据连续介质的选择，观察到方镁石的质量分数范围从最保守的情况下的2.7%到在约束较少的连续介质中的9%。此外，我们确定了一个功能在11.2微米的结晶硅酸盐镁橄榄石，只有一个小的贡献，从多环芳烃。5%的结晶硅酸盐部分需要高温，如那些在直接类星体环境中发现的，以抵消宇宙射线的快速破坏。
英文摘要：
We have determined the mineralogical composition of dust in the Broad Absorption Line (BAL) quasar PG 2112+059 using mid-infrared spectroscopy obtained with the Spitzer Space Telescope. From spectral fitting of the solid state features, we find evidence for Mg-rich amorphous silicates with olivine stoichiometry, as well as the first detection of corundum (Al_2O_3) and periclase (MgO) in quasars. This mixed composition provides the first direct evidence for a clumpy density structure of the grain forming region. The silicates in total encompass 56.5% of the identified dust mass, while corundum takes up 38 wt.%. Depending on the choice of continuum, a range of mass fractions is observed for periclase ranging from 2.7% in the most conservative case to 9% in a less constrained continuum. In addition, we identify a feature at 11.2 micron as the crystalline silicate forsterite, with only a minor contribution from polycyclic aromatic hydrocarbons. The 5% crystalline silicate fraction requires high temperatures such as those found in the immediate quasar environment in order to counteract rapid destruction from cosmic rays.
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