The most metal-poor galaxies
The most metal-poor galaxies
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DOI：
10.1007/s001590000005
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发表时间：
1999-11
期刊：
影响因子：
--
通讯作者：
D. Kunth;G. Östlin
中科院分区：
文献类型：
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作者：
D. Kunth;G. Östlin
金属丰度是控制恒星和星系形成和演化许多方面的关键参数。在这篇综述中，我们关注的是缺乏金属的星系，特别是最缺乏金属的星系，因为它们在宇宙景观中扮演着至关重要的角色。我们首先通过讨论定义全球金属丰度的困难问题以及如何测量给定星系的金属丰度来搭建舞台。控制星系中金属丰度的机制将被详细回顾，并涉及现代天体物理学的许多方面：星系的形成和演化，大质量星星的形成，恒星风，化学产额，流出和流入等。因为金属丰度大致与星系质量成比例，其中，最具代表性的，是《易经》。本文的核心是回顾我们在理解这些天体的性质和物理过程方面所取得的重大进展。讨论了它们之间的关系以及从一类物体到另一类物体的演化。在讨论一般的贫金属星系，我们提出了一个更详细的讨论一些非常贫金属的蓝色致密矮星系，如IZw 18。尽管大部分已知的知识都与我们的本地宇宙有关，但我们表明它与我们对原始星系的探索有关，并且与宇宙结构起源的问题有关。我们讨论了类星体吸收线和已知的遥远星系已经告诉我们什么？我们说明了恒星形成的贫金属星系的原始氦丰度的测定的重要性，它们的使用作为距离指示器，并讨论了可能性，以检测几乎无金属星系在高红移Lyemission。
Metallicity is a key parameter that controls many aspects in the formation and evolution of stars and galaxies. In this review we focus on the metal deficient galaxies, in particular the most metal-poor ones, because they play a crucial rôle in the cosmic scenery. We first set the stage by discussing the difficult problem of defining a global metallicity and how this quantity can be measured for a given galaxy. The mechanisms that control the metallicity in a galaxy are reviewed in detail and involve many aspects of modern astrophysics: galaxy formation and evolution, massive star formation, stellar winds, chemical yields, outflows and inflows etc. Because metallicity roughly scales as the galactic mass, it is among the dwarfs that the most metal-poor galaxies are found. The core of our paper reviews the considerable progress made in our understanding of the properties and the physical processes that are at work in these objects. The question on how they are related and may evolve from one class of objects to another is discussed. While discussing metal-poor galaxies in general, we present a more detailed discussion of a few very metal-poor blue compact dwarf galaxies like IZw18. Although most of what is known relates to our local universe, we show that it pertains to our quest for primeval galaxies and is connected to the question of the origin of structure in the universe. We discuss what do QSO absorption lines and known distant galaxies tell us already? We illustrate the importance of star-forming metal-poor galaxies for the determination of the primordial helium abundance, their use as distance indicator and discuss the possibility to detect nearly metal-free galaxies at high redshift from Lyemission.