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北美退伍军人节(Veterans Day),12 日无更新
arXiv 2009.07283astro-ph.GA
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莱曼α晕的物理起源和主要发射机制:来自TNG50模拟的结果与MUSE观测的比较

The physical origins and dominant emission mechanisms of Lyman-alpha halos: results from the TNG50 simulation in comparison to MUSE observations

Chris Byrohl, Dylan Nelson, Christoph Behrens, Ivan Kostyuk, Martin Glatzle, Annalisa Pillepich, Lars Hernquist, Federico Marinacci, Mark Vogelsberger

摘要:

扩展莱曼α发射现在通常通过叠加甚至在单个基础上在高红移星系周围检测到。尽管最近的观测进展,这些莱曼α晕(LAH)的物理起源,以及它们与星系,类星体,环星系气体和其他环境因素的关系仍然不清楚。我们提出的结果,从我们的新的莱曼α全辐射转移代码voroILTIS直接运行在非结构化Voronoi镶嵌宇宙流体动力学模拟。我们利用TNG 50模拟,从红移$z=2$到$z=5$模拟LAH,重点是用$8.0 < \log_{10}{(M_\star/\rm{M}_\odot)} < 10.5$模拟恒星形成星系。虽然TNG 50不直接跟随电离辐射,但它包括对活动星系核和具有自屏蔽的紫外线背景辐射的实时处理,这些都是影响气体冷却和电离的重要过程。在此基础上,我们给出了Ly $α$的径向表面亮度分布随星系质量和红移的函数关系。在$z>3$上与MUSE UDF的数据进行比较,结果显示出良好的一致性。我们测量了LAH大小和中心亮度与星系性质的相关性,发现在$8.5 \leq \log_{10} \left(M_\star/\rm{M}_\odot\right) \leq 9.5$的质量下,LAH的物理大小从$z=2$到$z=5$大致增加了一倍。最后,我们分解的配置文件从扩散发射和散射的光子从恒星形成区域的贡献。在我们的模拟中,我们发现恒星形成区域的再散射光子是观测到的LAH的主要来源。出乎意料的是,我们发现,在大半径的LAH配置文件的平坦化成为主导的光子来自其他附近的晕,而不是扩散发射本身。

英文摘要:

Extended Lyman-alpha emission is now commonly detected around high redshift galaxies through stacking and even on individual basis. Despite recent observational advances, the physical origin of these Lyman-alpha halos (LAHs), as well as their relationships to galaxies, quasars, circumgalactic gas, and other environmental factors remains unclear. We present results from our new Lyman-alpha full radiative transfer code voroILTIS which runs directly on the unstructured Voronoi tessellation of cosmological hydrodynamical simulations. We make use of the TNG50 simulation and simulate LAHs from redshift $z=2$ to $z=5$, focusing on star-forming galaxies with $8.0 < \log_{10}{(M_\star/\rm{M}_\odot)} < 10.5$. While TNG50 does not directly follow ionizing radiation, it includes an on-the-fly treatment for active galactic nuclei and ultraviolet background radiation with self-shielding, which are important processes impacting the cooling and ionization of the gas. Based on this model, we present the predictions for the stacked radial surface brightness profiles of Ly$α$ as a function of galaxy mass and redshift. Comparison with data from the MUSE UDF at $z>3$ reveals a promising level of agreement. We measure the correlations of LAH size and central brightness with galaxy properties, finding that at the masses of $8.5 \leq \log_{10} \left(M_\star/\rm{M}_\odot\right) \leq 9.5$, physical LAH sizes roughly double from $z=2$ to $z=5$. Finally, we decompose the profiles into contributions from diffuse emission and scattered photons from star-forming regions. In our simulations, we find rescattered photons from star-forming regions to be the major source in observed LAHs. Unexpectedly, we find that the flattening of LAH profiles at large radii becomes dominated by photons originating from other nearby halos rather than diffuse emission itself.

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