TNG100星系周介质中的高电离氧：分布、热状态与电离机制
Highly Ionized Oxygen in the Circumgalactic Medium of TNG100 Galaxies: Distributions, Thermal States, and Ionization Mechanisms
- School of Physics and Astronomy, Tel Aviv University（特拉维夫大学物理与天文学学院）
- Center for Computational Astrophysics, Flatiron Institute（平顿研究所计算天体物理学中心）
- Max-Planck-Institut für extraterrestrische Physik (MPE)（马克斯·普朗克地外物理学研究所）
- Department of Physics, University of California, Berkeley（加州大学伯克利分校物理系）
- Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过后处理TNG100模拟与解析建模，揭示了星系周介质中高电离氧（O VI、O VII、O VIII）的分布、热状态及电离机制，发现电离主导机制取决于晕维里温度与碰撞电离平衡峰值温度的关系。
AI中文摘要：
我们通过后处理Illustris TNG100模拟的输出并结合解析建模，研究了红移$z \approx 0$处星系周介质（CGM）中高电离氧物种O VI、O VII和O VIII的起源。我们的计算结果与观测大体一致，并提供了预测的平均氧离子柱密度作为晕维里质量函数的便捷函数拟合。我们确定了电子碰撞电离与由星系际辐射场产生的光致电离在产生这些离子（晕质量范围从$10^{10.5}$到$10^{14.5}$ M$_\odot$）中的相对作用。我们还确定了离子所处的热气体相：维里化热相、中间温度相或冷相。如果晕维里温度低于碰撞电离平衡（CIE）下离子分数达到最大时的气体温度，则光致电离主导整体CGM离子质量和柱密度。当光致电离占主导时，离子主要产生于激波加热的维里化相中。如果维里温度高于CIE下离子分数达到最大时的气体温度，则碰撞主导电离。然而，如果维里温度远高于离子的CIE峰值温度，则相当一部分离子质量可能存在于中间温度相中，而非热的维里化气体中。对于银河系质量晕，O VI和O VII由碰撞产生，O VIII由光致电离产生，三者均处于热的维里化相中。
英文摘要：
We investigate the origin of the highly ionized oxygen species, O VI, O VII, and O VIII, in the circumgalactic medium (CGM) of galaxies at redshifts $z \approx 0$, by post-processing the outputs of the Illustris TNG100 simulation alongside analytic modeling. Our computations are broadly consistent with observations, and we provide convenient functional fits for the predicted mean oxygen ion column densities as functions of halo virial mass. We determine the relative roles of electron impact collisional ionization versus photoionization by the metagalactic radiation field in producing the ions for halo masses ranging from $10^{10.5}$ to $10^{14.5}$~M$_\odot$. We also determine the thermal gas phases, virialized hot, intermediate temperature, or cool, within which the ions reside. If the halo virial temperature is below the gas temperature at which the ion fractions are maximal for collisional ionization equilibrium (CIE), then photoionization dominates the overall CGM ion mass and column density. When photoionization dominates, the ions are produced primarily in the shock heated virialized phase. If the virial temperature is above the gas temperatures at which the ion fractions are maximal for CIE, then collisions dominate the ionization. However, if the virial temperature is much larger than the ion CIE peak temperature a substantial portion of the ion mass may reside within the intermediate temperature phase as opposed to the hot virialized gas. For MW-mass halos, the O VI and O VII are produced collisionally, and the O VIII by photoionization, all three in the hot, virialized phase.
