Photodissociation and X-Ray-Dominated Regions
Photodissociation and X-Ray-Dominated Regions
复制标题
光解离和 X 射线主导区域
DOI：
10.1146/annurev-astro-052920-010254
复制
发表时间：
2022
影响因子：
33.3
通讯作者：
M. Chevance
中科院分区：
文献类型：
--
作者：
M. Wolfire;Livia Vallini;M. Chevance
来自恒星和活动星系核(AGN)的辐射产生了光解离区(PDR)和X射线主导区(XDR)，其中化学或加热分别由远紫外线(FUV)辐射或X射线辐射主导。PDR包括广泛的环境，从弥漫的星际介质到密集的恒星形成区域。XDR存在于拥有活动星系核的星系中心、原恒星盘和X射线双星附近。在这篇综述中，我们描述了PDR和XDR中主要的热、化学和辐射传输过程，并简要描述了模型及其在分析观测中的用途。然后，我们介绍了银河系、银河系外附近和高红移观测的最新结果。几个重要的结果包括：▪速度分辨PDR线揭示了中性原子气体的运动学，并提供了对恒星反馈过程的约束。然而，他们的解释存在争议，因为观察表明恒星风起着重要的作用，而它们在理论模型中的重要性要小得多。▪分子质量的一大部分存在于CO-暗气体中，特别是在低金属丰度和/或强辐射环境中。▪CO阶梯和[Ci][公式：见正文][CII]比率可以确定河外来源的ISM加热是由全紫外线还是X射线主导的。带有阿塔卡马大毫米/亚毫米阵列的▪，PDR和XDR示踪器现在可以在宇宙时间内在银河系尺度上进行常规探测。这使得将宇宙的恒星形成历史与气体的物理和化学性质的演化联系起来成为可能。预计《天文学与天体物理学年度评论》第60卷的最终在线出版日期为2022年8月。有关修订后的估计数字，请参阅http://www.annualreviews.org/page/journal/pubdates。
The radiation from stars and active galactic nuclei (AGNs) creates photodissociation regions (PDRs) and X-ray-dominated regions (XDRs), where the chemistry or heating are dominated by far-ultraviolet (FUV) radiation or X-ray radiation, respectively. PDRs include a wide range of environments, from the diffuse interstellar medium to dense star-forming regions. XDRs are found in the center of galaxies hosting AGNs, in protostellar disks, and in the vicinity of X-ray binaries. In this review, we describe the dominant thermal, chemical, and radiation transfer processes in PDRs and XDRs, as well as give a brief description of models and their use for analyzing observations. We then present recent results from Milky Way, nearby extragalactic, and high-redshift observations. Several important results include the following: ▪ Velocity-resolved PDR lines reveal the kinematics of the neutral atomic gas and provide constraints on the stellar feedback process. Their interpretation is, however, in dispute, as observations suggest a prominent role for stellar winds, whereas they are much less important in theoretical models. ▪ A significant fraction of molecular mass resides in CO-dark gas especially in low-metallicity and/or highly irradiated environments. ▪ The CO ladder and [Ci][Formula: see text][Cii] ratios can determine if FUV or X rays dominate the ISM heating of extragalactic sources. ▪ With Atacama Large Millimeter/submillimeter Array, PDR and XDR tracers are now routinely detected on galactic scales over cosmic time. This makes it possible to link the star-formation history of the Universe to the evolution of the physical and chemical properties of the gas. Expected final online publication date for the Annual Review of Astronomy and Astrophysics Volume 60 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.