Properties of the earliest galaxies

最早星系的特性

• 批准号: ST/F002742/1
• 负责人: Malcolm Bremer
• 金额: $ 43.11万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FF002742%2F1
• 关键词: Properties; earliest; galaxies

The gross cosmological parameters of the Universe that describe how fast it expands and how its expansion changes with time are thought to be known to a fair degree of accuracy. However, we do not have a deep understanding of the material of the Universe - the dark matter and dark energy that dominate over the ordinary ('baryonic') matter that is the familiar stuff of every-day life. We also don't understand the processes that cause this baryonic matter to form into structures such as planets, stars, galaxies, and clusters of galaxies. The purpose of the research to be funded by this grant is to gain some understanding of the largest-scale phenomena that affect the formation of structure by looking at the formation and evolution of galaxies and clusters of galaxies, and the internal substructure that they contain. Clusters of galaxies are often studied by their X-ray emission, which comes from hot gas held by the gravity field of their huge masses. At Bristol we also look at the gas in another way, by the 'shadow' that it casts against the microwave background radiation, which is a universal radiation field that was created soon after the Big Bang. Comparing the results from these ways of finding clusters tells us a lot more about the gas, and so about the mass holding the gas, than either technique alone. This trick is useful for discovering how much mass in the cluster is made up by dark matter and how much is baryonic matter, and whether these components of the mass of the cluster are distributed differently. Such a difference in distribution can occur in the cluster formation process, as it settles into a steady state, or later as the gas radiates energy away. We can also use the clusters that we find to study the expansion of the Universe itself, to find out more about the mysterious dark energy. There is a problem caused by the energy radiated by clusters - as the gas cools, it should drop inwards. But we see too little central gas - something is regulating the infall. It is thought that a major influence on the gas, and perhaps a source of all the energy needed to stop the infall, is the outflow of material from active galaxies, particularly radio galaxies, in the centres of the clusters. Active galaxies are galaxies where there seems to be a very massive black hole at their cores. These black holes themselves have the mass of a small galaxy, and are capable, somehow, of producing flows of gas at close to the speed of light away from themselves. This is a bit strange, since we normally think of black holes as being places where everything falls inwards, and the physics of how the outflows work, and how much energy they produce, is largely unknown. We need to measure that energy, and understand the physics of the process, in order to understand how black holes affect the clusters and galaxies in which they are located, and we will do much work on the radio, X-ray, infra-red properties of galaxy cores, and some theory, to try to understand what is going on. We expect to find out a lot about the black holes themselves, too. The most obvious feature of clusters of galaxies is the galaxies themselves, and we are also interested in knowing how galaxies form and change with time, why there are different types of galaxy, and how the galaxies affect the Universe as a whole. We have found that the stars in the earliest galaxies emit enough radiation to cause the entire Universe to change from being cold to being very hot, so that gas in the Universe changes from being neutral atoms to being a plasma, at a temperature like that of a star. How this happens, and what those first galaxies look like, is a focus of our research. We also want to know what happened to these early galaxies as they collided with one another, as their stars aged (and perhaps exploded), and as their central black holes kept pumping out energy, so we look also at nearby galaxies to study changes over the history of the Universe.

人们认为，描述宇宙膨胀速度以及膨胀随时间变化的宇宙总宇宙学参数在相当程度上是准确的。然而，我们对宇宙的物质——暗物质和暗能量——并没有深入的了解，而暗物质和暗能量主导着日常生活中常见的普通物质（“重子”）。我们也不了解导致这些重子物质形成行星、恒星、星系和星系团等结构的过程。这项研究的目的是通过观察星系和星系团的形成和演化，以及它们所包含的内部亚结构，来了解影响结构形成的最大规模现象。星系团通常通过它们的x射线发射来研究，这是由它们巨大质量的重力场所容纳的热气体产生的。在布里斯托尔，我们也用另一种方式观察气体，通过它在微波背景辐射下投下的“阴影”，这是一个宇宙大爆炸后不久产生的普遍辐射场。比较这些寻找星团的方法的结果，比单独使用任何一种技术都能告诉我们更多关于气体的信息，以及关于气体的质量。这个技巧对于发现星系团中有多少质量是由暗物质组成的，有多少是重子物质，以及星系团质量的这些组成部分是否分布不同是很有用的。这种分布上的差异可能发生在星团形成过程中，当它进入稳定状态时，或者后来气体辐射能量时。我们还可以利用我们发现的星系团来研究宇宙本身的膨胀，以发现更多关于神秘暗能量的信息。有一个问题是由星团辐射的能量引起的——当气体冷却时，它应该向内下降。但我们看到的中央气体太少了——有什么东西在调节着气体的流入。据认为，对气体的主要影响，也许是阻止气体流入所需的所有能量的来源，是活跃星系，特别是射电星系在星系团中心的物质流出。活动星系是指星系核心似乎有一个非常大的黑洞。这些黑洞本身具有一个小星系的质量，并且能够以某种方式产生接近光速的气体流。这有点奇怪，因为我们通常认为黑洞是所有东西都向内下落的地方，而流出的物理原理以及它们产生的能量在很大程度上是未知的。我们需要测量这种能量，了解这个过程的物理原理，以便了解黑洞是如何影响它们所在的星系团和星系的，我们将在无线电、x射线、星系核心的红外特性以及一些理论方面做很多工作，试图了解发生了什么。我们也希望能发现很多关于黑洞本身的信息。星系团最明显的特征是星系本身，我们也有兴趣了解星系是如何随着时间的推移而形成和变化的，为什么会有不同类型的星系，以及星系如何影响整个宇宙。我们发现，在最早的星系中，恒星发出的辐射足以使整个宇宙从寒冷变成非常热，因此宇宙中的气体从中性原子变成等离子体，温度与恒星相似。这是如何发生的，第一批星系是什么样子，是我们研究的重点。我们还想知道这些早期星系相互碰撞时发生了什么，当它们的恒星老化（也许爆炸）时，当它们的中心黑洞不断释放能量时，所以我们也观察附近的星系来研究宇宙历史的变化。

项目成果

Spectroscopic confirmation of a galaxy at redshift z = 8.6.

红移 z = 8.6 处星系的光谱确认。

• DOI: 10.1038/nature09462
• 发表时间: 2010
• 期刊: Nature
• 影响因子: 64.8
• 作者: Lehnert MD

LARGE-SCALE STRUCTURE TRACED BY MOLECULAR GAS AT HIGH REDSHIFT

高红移分子气体追踪的大型结构

• 发表时间: 2008
• 期刊: ASTROPHYSICAL JOURNAL LETTERS
• 影响因子: 7.9
• 作者: Stanway Elizabeth R.

Spectroscopy of z~ 5 Lyman break galaxies in the ESO Remote Galaxy Survey Spectroscopy of z ~ 5 Galaxies

ESO 远程星系巡天中 z~ 5 莱曼断裂星系的光谱 z ~ 5 星系光谱

• DOI: 10.1111/j.1365-2966.2010.17375.x
• 发表时间: 2010
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Douglas L

A limit on the number density of bright z â?? 7 galaxies

明亮 z 的数密度的限制 �??

• DOI: 10.1111/j.1365-2966.2008.13030.x
• 发表时间: 2008
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Stanway E

STAR FORMATION IN THE EARLY UNIVERSE: BEYOND THE TIP OF THE ICEBERG

• DOI: 10.1088/0004-637x/754/1/46
• 发表时间: 2012-01
• 期刊: The Astrophysical Journal
• 作者: N. Tanvir;A. Levan;A. Fruchter;J. Fynbo;J. Hjorth;K. Wiersema;M. Bremer;J. Rhoads;P. Jakobsson;P. O’Brien;E. Stanway;D. Bersier;P. Natarajan;P. Natarajan;J. Greiner;D. Watson;A. Castro‐Tirado;R. Wijers;R. Starling;K. Misra;J. Graham;C. Kouveliotou