arXiv 2402.014752024-02astro-ph.GA

磁场对星系周风–云系统吸收光谱的印记

The imprint of magnetic fields on absorption spectra from circumgalactic wind-cloud systems

Benedetta Casavecchia, Wladimir Banda-Barragan, Marcus Brueggen, Fabrizio Brighenti, Evan Scannapieco

备注：: 18 pages, 13 figures
发表信息：: A&A 689, A127 (2024)
DOI：: 10.1051/0004-6361/202449461

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AI总结：

本研究利用三维MHD模拟和PLUTO–TRIDENT合成光谱框架，揭示平行与横向磁场对星系周风–云系统形态、混合及吸收谱线的不同影响。

摘要：

星系风是探究恒星反馈如何调节星系质量与金属丰度的探针。观测表明，星系风是多相且磁化的。在局域宇宙中，密相由发射线和吸收线示踪，这些谱线揭示出嵌于热流中的快速运动云的存在。模拟告诉我们，磁场可以保护这些云并延缓其瓦解，但关于其观测效应的讨论很少。利用三维MHD模拟，我们研究了两种磁场取向（平行和横向）对云的形态、温度和密度结构、混合比例、离子运动学、柱密度以及吸收光谱的影响。我们研究了含辐射过程的超声速风–云系统，并开发了一个用于提取离子柱密度图和合成吸收光谱的框架。该框架依赖于研究离子族群，并通过一个利用YT、CLOUDY和STARBURST99将我们的PLUTO模拟与TRIDENT连接起来的接口来生成沿视线（down-the-barrel）光谱。我们发现，与平行情形相比，横向磁场使云变得不对称，屏蔽并保护致密冷气体，并降低混合比例。在横向磁场情形下，离子可以达到更高速度。磁场初始取向在合成光谱上的印记为：在冷相中，当磁场平行时，我们没有发现C ii和Si ii的特征；在由C iv和Si iv示踪的中间相中，我们发现横向情形下谱线更宽；在暖相中，我们发现平行情形下O vi和N v的谱线更深，但它们对磁场取向较不敏感。磁场显著影响冷云的吸收光谱。中间离子对磁场取向最敏感，并有可能提供有关磁场拓扑的信息。

英文摘要：

Galactic winds probe how stellar feedback regulates the mass and metallicity of galaxies. Observations show that galactic winds are multiphase and magnetised. In the local Universe, the dense phase is traced by emission and absorption lines, which reveal the presence of fast-moving clouds embedded in hot streams. Simulations tell us that magnetic fields can shield such clouds and delay their disruption, but there is little discussed on their observational effects. Using 3D MHD simulations, we study the influence of two orientations of the magnetic field (aligned and transverse) on the cloud morphology, temperature and density structure, mixing fraction, ion kinematics, column densities, and absorption spectra. We study supersonic wind-cloud systems with radiative processes, and develop a framework to extract ion column density maps and synthetic absorption spectra. The framework relies on studying ion populations and creating down-the-barrel spectra via an interface that links our PLUTO simulations to TRIDENT using YT, CLOUDY, and STARBURST99. We find that the transverse magnetic field makes the cloud asymmetric, shields and protects dense cold gas, and reduces mixing fractions compared to the aligned case. Ions can reach higher velocities in the transverse field case. The imprints of the initial orientation of the field on the synthetic spectra are: in the cold phase we find no signature of C ii and Si ii when the field is aligned, in the intermediate phase traced by C iv and Si iv we find broader lines in the transverse case, and in the warm phase we find deeper lines for O vi and N v in the aligned case, but they are less sensitive to the field orientation. Magnetic fields significantly affect the absorption spectra of cold clouds. Intermediate ions are the most sensitive to the magnetic field orientation and can potentially yield information about magnetic field topology.

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