arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1901.04510astro-ph.GA
收藏

高$-$ z光学薄C III吸收体中的物理条件：云大小的起源和相关的相关性

Physical conditions in high$-$z optically thin C III absorbers: Origin of cloud sizes and associated correlations

Abhisek Mohapatra, R. Srianand, Vikram Khaire, Ananta C. Pradhan

备注：
22 pages, 16 figures, 8 tables, accepted for publishing in MNRAS
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

我们提出了详细的光致电离模型以及对齐的光学薄C III吸收组件在$2.1 < z < 3.4$。使用我们的模型，我们估计密度（$n_{\rm \tiny H}$），金属丰度（$[C/H]$），总氢柱密度和视线厚度（$L$）在每个C III组件。我们估计的系统误差，在这些数量的贡献的类星体光谱指数的允许范围内使用的紫外背景辐射计算。我们推断的$n_{\rm \tiny H}$和超密度（$Δ$）远高于文献中的测量值，有利于来自环星系介质相关气体的吸收，可能不处于流体静力平衡。我们还注意到与C Ⅲ组分相关的$n_{\rm \tiny H}$、$L$和$[C/H]$都表现出统计学上显著的红移演化。在某种程度上，这些红移演变是由仅在低端$-z$中出现的紧凑、高$n_{\rm \tiny H}$和高$[C/H]$分量驱动的。发现$[C/H]$与$L$、$L$与中性氢柱密度（N（HI））、N（HI）与$[C/H]$之间存在5个以上的$σ$水平的相关性。我们表明，$L$与$[C/H]$的相关性可以很好地再现，如果$L$是由气体冷却时间和声速的产品，如预期的情况下，云破碎热不稳定性。这使我们能够通过简单的光电离考虑来解释其他观察到的相关性。在大的$z$范围内研究光学薄的C III吸收体，并将它们的$z$演化与全球恒星形成率密度演化联系起来，可以揭示环星系介质中冷团形成及其演化的物理机制。

英文摘要：

We present detailed photoionization models of well aligned optically thin C III absorption components at $2.1 < z < 3.4$. Using our models we estimate density ($n_{\rm \tiny H}$), metallicity ($[C/H]$), total hydrogen column density and line-of-sight thickness ($L$) in each C III components. We estimate the systematic errors in these quantities contributed by the allowed range of the quasar spectral index used in the ultraviolet background radiation calculations. Our inferred $n_{\rm \tiny H}$ and overdensity ($Δ$) are much higher than the measurements available in the literature and favor the absorption originating from gas associated with circumgalactic medium and probably not in hydrostatic equilibrium. We also notice $n_{\rm \tiny H}$, $L$ and $[C/H]$ associated with C III components show statistically significant redshift evolution. To some extent, these redshift evolutions are driven by the appearance of compact, high $n_{\rm \tiny H}$ and high $[C/H]$ components only in the low$-z$ end. We find more than 5$σ$ level correlation between $[C/H]$ and $L$, $L$ and neutral hydrogen column density (N (HI)), N (HI) and $[C/H]$. We show $L$ versus $[C/H]$ correlation can be well reproduced if $L$ is governed by the product of gas cooling time and sound speed as expected in the case of cloud fragmentation under thermal instabilities. This allows us to explain other observed correlations by simple photoionization considerations. Studying the optically thin C III absorbers over a large $z$ range and probably correlating their $z$ evolution with global star formation rate density evolution can shed light into the physics of cold clump formation and their evolution in the circumgalactic medium.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑