The interstellar oxygen crisis, or where have all the oxygen atoms gone?
The interstellar oxygen crisis, or where have all the oxygen atoms gone?
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星际氧危机，或者说所有的氧原子都到哪里去了？
DOI：
10.1093/mnras/stv1900
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发表时间：
2015
影响因子：
4.8
通讯作者：
Jiang B. W.
中科院分区：
文献类型：
--
作者：
Wang Shu;Li Aigen;Jiang B. W.
星际介质（ISM）似乎有显着过剩的氧气，这被称为“O危机”：与采用的星际参考丰度无关，从气相中消耗的O原子总数远远超过固体中的O原子总数高达~ 160 ppm O/H。最近，有人假设失踪的O可能隐藏在微米大小的H2O冰粒中。我们检查这一假设，通过比较红外（IR）消光和远红外发射所产生的这些颗粒与银河弥漫ISM中观察到的。我们发现，这是可能的弥漫ISM容纳约160 ppm的O/H在微米级的H2O冰粒，而不违反观测的限制，包括3.1微米的O-H吸收功能的缺乏。更具体地说，半径约4微米且O/H = 160 ppm的H2O冰粒能够解释在约3-8微米处观察到的平坦消光，并且在远红外中不会产生过量发射。这些颗粒可能存在于漫ISM中通过致密分子云之间的快速物质交换而形成，而漫云则被光溅射破坏。
The interstellar medium (ISM) seems to have a significant surplus of oxygen which was dubbed as the "O crisis": independent of the adopted interstellar reference abundance, the total number of O atoms depleted from the gas phase far exceeds that tied up in solids by as much as ~160ppm of O/H. Recently, it has been hypothesized that the missing O could be hidden in micrometer-sized H2O ice grains. We examine this hypothesis by comparing the infrared (IR) extinction and far-IR emission arising from these grains with that observed in the Galactic diffuse ISM. We find that it is possible for the diffuse ISM to accommodate ~160ppm of O/H in micron-sized H2O ice grains without violating the observational constraints including the absence of the 3.1micron O-H absorption feature. More specifically, H2O ice grains of radii ~4micron and O/H = 160 ppm are capable of accounting for the observed flat extinction at ~ 3-8 micron and produce no excessive emission in the far-IR. These grains could be present in the diffuse ISM through rapid exchange of material between dense molecular clouds where they form and diffuse clouds where they are destroyed by photosputtering.