论文标题
星际灭绝和元素丰度
Interstellar Extinction and Elemental Abundances
论文作者
论文摘要
星际介质（ISM）中的元素以气体或灰尘形式存在。星际灭绝和元素丰度对星际灰尘的组成，大小和数量提供了关键的约束。大多数灭绝建模工作都假定了粉尘形成元素的总丰度（包括气体和灰尘） - 称为“星际丰富性”，“星际参考丰度”或“宇宙丰度” - - - - - - - 求解和固定的气相丰度，以独立于群体群。但是，尚不清楚太阳丰度是否是星际丰度的适当表示。同时，已知气相丰度与局部星际环境表现出明显的变化。在这项工作中，我们探讨了B恒星，太阳能和原始般的丰度的丰富性的生存能力，以及由银河化学富集（GCE）增强的原始极值，作为在数量上通过数量地审查所有范围众多范围的巨大和元素的范围，以表现出十个星际线的范围，并构成十大群体的范围。在观察上确定了元素（即C，O，Mg，Si和Fe）。与其假设一个特定的灰尘模型，然后拟合观察到的灭绝曲线，对于每个视线，我们应用了独立于模型的kramers-kronig关系，该关系将波长整合的灭绝与总灰尘体积相关联，以对尘埃耗尽的下限。这与观察衍生的气相丰度一起，使我们能够排除B-Star，太阳能和原始物质丰度作为星际参考标准。我们得出的结论是，GCE的原始极丰度是星际丰度的可行表示。
Elements in the interstellar medium (ISM) exist in the form of gas or dust. The interstellar extinction and elemental abundances provide crucial constraints on the composition, size and quantity of interstellar dust. Most of the extinction modeling efforts have assumed the total abundances (both in gas and in dust) of the dust-forming elements---known as the "interstellar abundances", the "interstellar reference abundances", or the "cosmic abundances"---to be solar and the gas-phase abundances to be independent of the interstellar environments. However, it remains unclear if the solar abundances are an appropriate representation of the interstellar abundances. Meanwhile, the gas-phase abundances are known to exhibit appreciable variations with the local interstellar environments. In this work we explore the viability of the abundances of B stars, the solar and protosolar abundances, and the protosolar abundances augmented by Galactic chemical enrichment (GCE) as an appropriate representation of the interstellar abundances by quantitatively examining the extinction and elemental abundances of ten interstellar lines of sight for which both the extinction curves and the gas-phase abundances of all the major dust-forming elements (i.e., C, O, Mg, Si and Fe) have been observationally determined. Instead of assuming a specific dust model and then fitting the observed extinction curves, for each sightline we apply the model-independent Kramers-Kronig relation, which relates the wavelength-integrated extinction to the total dust volume, to place a lower limit on the dust depletion. This, together with the observationally-derived gas-phase abundances, allows us to rule out the B-star, solar, and protosolar abundances as the interstellar reference standard. We conclude that the GCE-augmented protosolar abundances are a viable representation of the interstellar abundances.
