Blue galaxies: modelling nebular He ii emission in high redshift galaxies
Blue galaxies: modelling nebular He ii emission in high redshift galaxies
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蓝色星系：模拟高红移星系中的星云 He ii 发射
DOI：
10.1093/mnras/stz3290
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发表时间：
2019
影响因子：
4.8
通讯作者：
Kirk S. S. Barrow
中科院分区：
文献类型：
--
作者：
Kirk S. S. Barrow
使用宇宙学模拟来做出有用的、科学相关的发射线预测是一个相对较新且快速发展的领域。然而，星云发射线的建模特别具有挑战性，因为它们对局部光电离平衡极其敏感，而局部光电离平衡可能是由恒星在尘埃和气体的不均匀吸收介质中的空间分散分布驱动的。因此，文献中存在观察到的发射线图案中的几个未建模的谜团。例如，有一些问题是为什么低金属丰度矮星系观测中的 He ii λ4686/H β 比率往往高于模型预测。由于流体动力学宇宙学模拟最适合这种质量和金属丰度状态，因此这个问题为开发稳健的发射线建模管道提供了一个很好的测试用例。这项工作中描述的流程可以对产生高 He ii λ4686/H β 比率的过程进行建模，并消除比率低于 3% 的一些建模差异，而不包括 AGN、X 射线双星、高质量双星或头重脚轻的恒星初始质量函数。人们发现，这些比率对恒星形成历史中 15 Myr 或更长间隙的存在比对异常电离参数或特定恒星形成速率更敏感。它们也与大质量恒星的 WR 阶段密切对应。除了对 He ii λ4686/H β 比率的研究之外，这项工作还为下一代星云发射线建模研究绘制了总体路径。
Using cosmological simulations to make useful, scientifically relevant emission line predictions is a relatively new and rapidly evolving field. However, nebular emission lines have been particularly challenging to model because they are extremely sensitive to the local photoionization balance, which can be driven by a spatially dispersed distribution of stars amidst an inhomogeneous absorbing medium of dust and gas. As such, several unmodelled mysteries in observed emission line patterns exist in the literature. For example, there is some question as to why He ii λ4686/H β ratios in observations of lower metallicity dwarf galaxies tend to be higher than model predictions. Since hydrodynamic cosmological simulations are best suited to this mass and metallicity regime, this question presents a good test case for the development of a robust emission line modelling pipeline. The pipeline described in this work can model a process that produces high He ii λ4686/H β ratios and eliminate some of the modelling discrepancy for ratios below 3 per cent without including AGNs, X-ray binaries, high mass binaries, or a top-heavy stellar initial mass function. These ratios are found to be more sensitive to the presence of 15 Myr or longer gaps in the star formation histories than to extraordinary ionization parameters or specific star formation rates. They also closely correspond to the WR phase of massive stars. In addition to the investigation into He ii λ4686/H β ratios, this work charts a general path forward for the next generation of nebular emission line modelling studies.
影响因子：
2.5
作者：
K. Olsen;A. Pallottini;A. Wofford;Marios Chatzikos;Mitchell Revalski;F. Guzm'an;G. Popping;E. V'azquez-Semadeni;G. Magdis;M. Richardson;M. Hirschmann;W. Gray
通讯作者：
K. Olsen;A. Pallottini;A. Wofford;Marios Chatzikos;Mitchell Revalski;F. Guzm'an;G. Popping;E. V'azquez-Semadeni;G. Magdis;M. Richardson;M. Hirschmann;W. Gray