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Implementation of metals in a three-dimensional non-LTE radiative transfer code to simulate the intergalactic medium at early cosmological times

在三维非 LTE 辐射传输代码中实现金属，以模拟早期宇宙学时代的星际介质

基本信息

批准号：
238098171
负责人：
Professor Dr. Adalbert Wilhelm Alois Pauldrach (†)
金额：
--
依托单位：
Lehrstuhl für Theoretische und Numerische Astrophysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/238098171?language=en
关键词：
Implementation metals three dimensional non

项目摘要

An important issue in modern astrophysical research is to understand precisely the early phases of the evolution of the universe. Recent studies investigating the formation of large-scale structures have shown that the first generation of stars, formed directly from the primordial gas, already played a crucial role during the early phase of the epoch of reionization of the universe. Theoretical studies indicate that the initial mass function (IMF) of this first stellar population differed significantly from the present IMF, being top-heavy and thus allowing for the presence of supermassive stars. The first generation of population III stars was therefore not only very luminous, but due to its lack of metals its output of UV radiation considerably exceeded the UV emission of present stars. Because of their short lifetimes the metals produced in their cores were quickly returned to the environment from which early population II stars with different IMFs and different spectral energy distributions (SEDs) were formed, already much earlier than the time at which the universe became completely reionized (at a redshift of z > 6).In the proposed project we aim to calculate SEDs of very massive stars of different metallicities as input for the 3-dimensional radiative transfer code we are currently developing to simulate the temporal evolution of the ionization of the inhomogeneous interstellar and intergalactic medium, using multiple stellar clusters as sources of ionizing radiation. The objective is not only to simulate the processes which are believed to have lead to the reionized state of the universe, but also to determine possible observational diagnostics to constrain the nature of the ionizing sources. The multi-frequency treatment in our combination of 3-dimensional radiative transfer -- based on ray-tracing -- and time dependent simulation of the ionization structure of all important elements -- including metals -- will allow, in principle, to deduce information about the spectral characteristics of the first generations of stars and their interaction with the surrounding gas on various scales. As our tool will be able to handle distributions of numerous radiative sources characterized by high resolution synthetic SEDs (we will thus not simply use ``black-body'' spectra), and will also yield occupation numbers of the most important energy levels of the elements which will be treated in NLTE and calculated consistently with the 3-dimensional radiative transfer, the ionization state of an inhomogeneous gaseous density structure will be calculated more accurately. On basis of this procedure we will systematically investigate the impact of the increasing metallicity of the radiative sources (simulated cluster structures) in the transition from population III stars to population II/I stars on the ionization structure of the interstellar and intergalactic medium.

现代天体物理学研究中的一个重要问题是精确地了解宇宙演化的早期阶段。最近调查大规模结构形成的研究表明，直接由原始气体形成的第一代恒星在宇宙再电离时代的早期阶段已经发挥了关键作用。理论研究表明，这第一个恒星群的初始质量函数（IMF）与现在的IMF有很大的不同，它是头重的，因此允许超大质量恒星的存在。因此，第一代星族III恒星不仅非常明亮，而且由于其缺乏金属，其紫外线辐射的输出大大超过了目前恒星的紫外线辐射。由于它们的寿命很短，在它们的核心产生的金属很快就回到了形成不同imf和不同光谱能量分布（SEDs）的早期II星族恒星的环境中，这已经比宇宙完全再电离的时间早得多（红移为z >.6）。在提议的项目中，我们的目标是计算不同金属丰度的超大质量恒星的SEDs，作为我们目前正在开发的三维辐射传输代码的输入，以模拟非均匀星际和星系间介质电离的时间演化，使用多个星团作为电离辐射源。目的不仅是模拟被认为导致宇宙再电离状态的过程，而且还要确定可能的观测诊断，以限制电离源的性质。我们结合了三维辐射传输的多频率处理——基于光线追踪——以及所有重要元素（包括金属）的电离结构的时间依赖模拟，原则上，将允许推断出关于第一代恒星的光谱特征及其与周围气体在不同尺度上的相互作用的信息。由于我们的工具将能够处理以高分辨率合成SEDs为特征的众多辐射源的分布（因此我们将不简单地使用“黑体”光谱），并且还将产生将在NLTE中处理并与三维辐射传递一致计算的元素的最重要能级的占用数，因此将更准确地计算非均匀气体密度结构的电离状态。在此基础上，我们将系统地研究III星向II/I星过渡过程中辐射源（模拟星团结构）金属丰度的增加对星际和星系间介质电离结构的影响。