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arXiv 0804.4236astro-ph
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本地星际介质中的奇异云

Exotic clouds in the local interstellar medium

Snezana Stanimirovic

备注：
10 pages, refereed, accepted for publication in the proceedings of the "From the Outer Heliosphere to the Local Bubble: Comparisons of New Observations with Theory" conference, Space Science Reviews
发表信息：
Space Sci.Rev.143:291-301,2009
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摘要：

局域泡（LB）内的中性星际介质（ISM）具有典型的暖中性介质（WNM）性质。然而，最近的几个中性氢（HI）吸收实验表明，至少有几个冷扩散云内或边界的LB的存在的证据，与传统的冷中性介质的属性非常不寻常。这些冷云具有低的HI柱密度和AU尺度大小。由于LB内部冷气体和暖气体的运动学相似，这表明所有这些不同口味的局部ISM可能属于同一星际流。LB内部的温相和冷相的共存是令人兴奋的，因为它可以用来探测LB内部的热压。除了冷云，几个离散的屏幕电离散射材料清楚地位于LB内。LB内部的冷外来云很可能是长寿的，我们预计未来将通过更灵敏的无线电观测发现更多具有类似性质的云。虽然对产生这种云的物理机制仍然知之甚少，但相位转换和/或星际湍流的动态触发可能发挥重要作用。

英文摘要：

The neutral interstellar medium (ISM) inside the Local Bubble (LB) has been known to have properties typical of the warm neutral medium (WNM). However, several recent neutral hydrogen (HI) absorption experiments show evidence for the existence of at least several cold diffuse clouds inside or at the boundary of the LB, with properties highly unusual relative to the traditional cold neutral medium. These cold clouds have a low HI column density, and AU-scale sizes. As the kinematics of cold and warm gas inside the LB are similar, this suggests a possibility of all these different flavors of the local ISM belonging to the same interstellar flow. The co-existence of warm and cold phases inside the LB is exciting as it can be used to probe the thermal pressure inside the LB. In addition to cold clouds, several discrete screens of ionized scattering material are clearly located inside the LB. The cold exotic clouds inside the LB are most likely long-lived, and we expect many more clouds with similar properties to be discovered in the future with more sensitive radio observations. While physical mechanisms responsible for the production of such clouds are still poorly understood, dynamical triggering of phase conversion and/or interstellar turbulence are likely to play an important role.

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