arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2012.11645astro-ph.GAastro-ph.CO
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Ly $α$发射体的高红移观测

Observations of Ly$α$ Emitters at High Redshift

Masami Ouchi

摘要:

在这一系列讲座中,我回顾了我们对高$z$ Ly $α$发射体(LAEs)的观察理解和相关的科学主题。自20世纪90年代末发现LAE以来,已在$z\sim 0$至$z\sim 10$通过光度(光谱)鉴定了一万多个LAE。这些大型LAEs样本有助于解决两个主要的天体物理学问题,星系形成和宇宙再电离。统计研究揭示了LAEs的物理特性:年轻的恒星星族、显著的光度函数演化、致密的形貌、低金属/尘埃含量的高电离星际介质(ISM)、低质量的暗物质晕。典型的LAE代表低质量高$z$星系,矮星系的高$z$类似物,其中一些被认为是第III族星系的候选者。这些观测研究还精确定位了罕见的明亮的Ly $α$源,其延伸超过$\sim 10-100$ kpc,被称为Ly $α$斑点,其物理起源正在争论中。LAEs通过星系间介质(IGM)中性氢对Ly $α$的阻尼翼吸收,作为宇宙再电离历史的探针,补充了宇宙微波背景辐射和21 cm观测。LAE的低质量和高电离的人口可能是宇宙再电离的主要来源。宇宙再电离的电离光子的预算已经受到限制,尽管在参数上仍然存在很大的观测不确定性。除了星系形成和宇宙再电离之外,LAEs在科学前沿领域的一些新用途已经被提出,例如环星系介质中{ \sc Hi}气体的分布和大尺度结构的细丝。正在进行的计划和未来的望远镜项目,如JWST,ELT和SKA,将推动科学前沿的视野。

英文摘要:

In this series of lectures, I review our observational understanding of high-$z$ Ly$α$ emitters (LAEs) and relevant scientific topics. Since the discovery of LAEs in the late 1990s, more than ten (one) thousand(s) of LAEs have been identified photometrically (spectroscopically) at $z\sim 0$ to $z\sim 10$. These large samples of LAEs are useful to address two major astrophysical issues, galaxy formation and cosmic reionization. Statistical studies have revealed the general picture of LAEs' physical properties: young stellar populations, remarkable luminosity function evolutions, compact morphologies, highly ionized inter-stellar media (ISM) with low metal/dust contents, low masses of dark-matter halos. Typical LAEs represent low-mass high-$z$ galaxies, high-$z$ analogs of dwarf galaxies, some of which are thought to be candidates of population III galaxies. These observational studies have also pinpointed rare bright Ly$α$ sources extended over $\sim 10-100$ kpc, dubbed Ly$α$ blobs, whose physical origins are under debate. LAEs are used as probes of cosmic reionization history through the Ly$α$ damping wing absorption given by the neutral hydrogen of the inter-galactic medium (IGM), which complement the cosmic microwave background radiation and 21cm observations. The low-mass and highly-ionized population of LAEs can be major sources of cosmic reionization. The budget of ionizing photons for cosmic reionization has been constrained, although there remain large observational uncertainties in the parameters. Beyond galaxy formation and cosmic reionization, several new usages of LAEs for science frontiers have been suggested such as the distribution of {\sc Hi} gas in the circum-galactic medium and filaments of large-scale structures. On-going programs and future telescope projects, such as JWST, ELTs, and SKA, will push the horizons of the science frontiers.

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