Three-dimensional modeling of ionized gas - II. Spectral energy distributions of massive and very massive stars in stationary and time-dependent modeling of the ionization of metals in H ii regions
Three-dimensional modeling of ionized gas - II. Spectral energy distributions of massive and very massive stars in stationary and time-dependent modeling of the ionization of metals in H ii regions
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电离气体的三维建模 - II 在 H ii 区域金属电离的固定和时间相关建模中大质量和超大质量恒星的光谱能量分布
DOI：
10.1051/0004-6361/201424976
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发表时间：
2015
影响因子：
6.5
通讯作者：
Hoffmann T. L.
中科院分区：
文献类型：
--
作者：
Weber J. A;Pauldrach A. W. A.;Hoffmann T. L.
ContextH ii区域在测量星际介质的化学成分方面发挥着至关重要的作用，并提供了有关约束银河系化学演化模型的元素丰度的基本数据。观测到的发射线强度和星云模型预测的发射线强度之间仍然存在差异，这可以部分归因于模型中使用的电离辐射源的光谱能量分布（SED）以及星云modeling.AimsOne的简化假设对星云光谱的主要影响是金属丰度，星云和恒星，这表明即使在附近的星系之间也存在很大的变化。虽然星云建模经常涉及测试不同的星云金属丰度对预测光谱的影响，但仍然缺乏足够的恒星大气网格和不同金属丰度的真实SED。这是不幸的，因为恒星金属丰度对星云谱线强度比的影响，通过它对SED的影响，与星云金属丰度的变化具有相似的重要性。为了克服这一缺陷，我们计算了一个网格的模型大气的SED的大质量和非常大质量的O型恒星覆盖范围的金属丰度从显着的太阳下（0.1Z）到超日（2Z）。考虑到所有重要元素的谱线对电离通量的衰减和辐射的流体动力学的art模式大气代码驱动风及其对SED的影响。对于评估的SEDs在星云模拟，我们已经开发了一个（迄今为止不可用）3D辐射传输代码，其中包括一个依赖于时间的治疗的金属ionization.ResultsUsing的SEDs在1D和3D星云models，我们探索恒星金属丰度，气体金属丰度，和气体的不均匀性对星云电离结构和发射线强度的相对影响。我们发现，恒星和气体金属丰度是类似的重要性，建立线强度比通常用于星云诊断，而气体的不均匀性只有从属的影响，对全球线emission.ConclusionsNebular诊断作为定量工具，用于测量的丰度在星际气体可以用来充分发挥其潜力，只有当影响的SED，金属丰度，和星云的几何结构。为了这些目的，详细的恒星SED像我们的网格是用于预测星云发射线光谱的光电离模型的一个重要组成部分。
ContextH ii regions play a crucial role in the measurement of the chemical composition of the interstellar medium and provide fundamental data about element abundances that constrain models of galactic chemical evolution. Discrepancies that still exist between observed emission line strengths and those predicted by nebular models can be partly attributed to the spectral energy distributions (SEDs) of the sources of ionizing radiation used in the models as well as to simplifying assumptions made in nebular modeling.AimsOne of the main influences on the nebular spectra is the metallicity, both nebular and stellar, which shows large variations even among nearby galaxies. Although nebular modeling often involves testing of different nebular metallicities against their influence on the predicted spectra, adequate grids of stellar atmospheres and realistic SEDs for different metallicities are still lacking. This is unfortunate because the influence of stellar metallicity on nebular line strength ratios, via its effect on the SEDs, is of similar importance as variations in the nebular metallicity. To overcome this deficiency we have computed a grid of model atmosphere SEDs for massive and very massive O-type stars covering a range of metallicities from significantly subsolar (0.1Z⊙) to supersolar (2Z⊙).MethodsThe SEDs have been computed using a state-of-the-art model atmosphere code that takes into account the attenuation of the ionizing flux by the spectral lines of all important elements and the hydrodynamics of the radiatively driven winds and their influence on the SEDs. For the assessment of the SEDs in nebular simulations we have developed a (heretofore not available) 3D radiative transfer code that includes a time-dependent treatment of the metal ionization.ResultsUsing the SEDs in both 1D and 3D nebular models we explore the relative influence of stellar metallicity, gas metallicity, and inhomogeneity of the gas on the nebular ionization structure and emission line strengths. We find that stellar and gas metallicity are of similar importance for establishing the line strength ratios commonly used in nebular diagnostics, whereas inhomogeneity of the gas has only a subordinate influence on the global line emission.ConclusionsNebular diagnostics as a quantitative tool for measuring the abundances in the interstellar gas can be used to its full potential only when the influence of SEDs, metallicity, and geometric structure of the nebula are taken into account. For these purposes, detailed stellar SEDs like those of our grid are an essential ingredient for the photoionization models used to predict nebular emission line spectra.
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2007
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