Supermassive Black-Holes in Formation and their Role in Galaxy Evolution

我们的宇宙包含数十亿个像我们银河系一样的星系，每个星系的中心都有一个超大质量黑洞。今天最大的星系重量超过我们太阳质量的万亿倍，超大质量黑洞的重量相当于十亿个太阳。但是这些星系和黑洞是怎么变得这么大的呢？宇宙已经有140亿年的历史了，但星系的主要增长发生在100多亿年前。理论预测，我们宇宙历史上的这一时期的特征是小星系的剧烈碰撞。这些碰撞压缩了星系中的气体形成恒星，新的恒星为超大质量黑洞提供了燃料，今天的大质量星系在它们的中心聚集了巨大的黑洞。尽管星系形成的图像被广泛接受，但我们仍然没有观察到许多这些过程的发生，特别是在100多亿年前我们宇宙历史上非常活跃的增长时期。我们想捕捉最大质量的星系和超大质量黑洞，因为它们正在成长，但这些系统是非常罕见的;寻找它们相当于大海捞针！我们不仅需要能够扫描整个天空的精密望远镜来寻找这些巨型星系，还需要足够灵敏的望远镜来探测从星系最初形成时经过数十亿年才到达我们今天的光线。直到最近才成为可能，新的数码相机已经安装在世界上一些最大的望远镜上，以提供覆盖大部分天空的敏感图像。我正在研究这些新的数字成像调查的数据。我的研究涉及扫描数字图像，以定位我们宇宙中最巨大的星系，因为它们正在经历一个主要的增长。我已经在遥远的宇宙中发现了第一个超大质量的成长星系。通过对这些新发现的星系进行高分辨率成像，我们将能够观察它们内部发生的各种物理过程以及超大质量黑洞如何影响这些过程。在我们新的天空数字图像中，隐藏着更罕见的系统，例如宇宙中的第一个星系和超大质量黑洞，其历史可以追溯到宇宙只有5亿年的时候。我们现在能够观察这些星系，因为它们开始第一次为它们的超大质量黑洞提供食物，这是它们成长为今天的怪物黑洞的旅程。观测这个第一次的进食阶段对于理解超大质量黑洞是如何成长的是至关重要的，大多数的数字成像巡天都是在电磁波谱的可见光部分探测星系发出的星光。然而，星系中的尘埃可以吸收可见光，然后以较长的红外波长重新辐射。因此，红外线数据可以提供星系中星星形成的最公正的观点。利用跟踪红外波长光的新调查，我的研究将测量在遥远星系中形成的恒星数量，这些星系正在积极喂养超大质量黑洞。我们的目标是确定超大质量黑洞是否直接影响星系形成恒星的速度，从而控制其宿主星系最终会变成多大的质量。综上所述，我的研究旨在通过直接观察大质量星系和超大质量黑洞在早期宇宙中的组装过程，建立大质量星系和超大质量黑洞形成的连贯观测图像。这将通过汇集目前正在进行的一些最大的电磁频谱天文调查的新数据来实现。

Our Universe contains billions of galaxies like our own Milky Way, each harbouring a supermassive black-hole at its centre. The biggest galaxies today weigh more than a trillion times the mass of our Sun with supermassive black-holes weighing the equivalent of a billion Suns. But how did these galaxies and black-holes get so big? The Universe is almost 14 billion years old but the major growth spurt of galaxies took place more than ten billion years ago. Theory predicts that this epoch in our Universe's history was characterized by violent collisions of small galaxies. These collisions compressed the gas in galaxies to form stars, the new stars provided fuel for the supermassive black-holes to feed on and the massive galaxies of today were assembled with enormous black-holes at their centres.Despite this well-accepted picture of galaxy formation we still have not observed many of these processes happening, particularly during the very active period of growth in our Universe's history more than 10 billion years ago. We want to catch the most massive galaxies and supermassive black-holes as they are growing but these systems are very rare; looking for them is comparable to looking for a needle in a haystack! Not only do we need sophisticated telescopes that can scan the entire sky searching for these monster galaxies, they also need to be sensitive enough to detect light that has traveled billions of years from when the galaxies were first forming, to reach us today. This has only recently become possible and new digital cameras have been mounted on some of the largest telescopes in the world to provide sensitive images covering most of the sky. I am working on data from several of these new digital imaging surveys.My research involves scanning the digital images to locate the most enormous galaxies in our Universe as they are undergoing a major growth spurt. I have already identified the first of these ultra-massive growing galaxies in the distant Universe. Through high-resolution imaging of these newly discovered galaxies, we will be able to observe the various physical processes going on within them and how the supermassive black-hole is affecting these processes.Within our new digital images of the sky lurk even rarer systems such as the first galaxies and supermassive black-holes in our Universe dating back to when the Universe was only 500 million years old. We are now able to watch these galaxies as they begin to feed their supermassive black-hole for the first time on their journey to growing to the monster black-holes of today. Observing this first feeding phase is critical for building up an understanding of how supermassive black-holes grow.Most digital imaging surveys detect starlight from galaxies in the visible portion of the electromagnetic spectrum. However, dust in galaxies can absorb visible light, which is then re-radiated at the longer infrared wavelengths. Infrared data therefore allows the most unbiased view of star formation in galaxies. Utilising new surveys that trace light at infrared wavelengths, my research will measure the number of stars being formed in distant galaxies with actively feeding supermassive black holes. The aim is to determine if the supermassive black-hole directly impacts the rate at which a galaxy is forming stars, therefore controlling how massive its host galaxy will eventually become.Taken together my research aims to build up a coherent observational picture of the formation of massive galaxies and supermassive black-holes by directly observing them as they are being assembled in the early Universe. This will be done by bringing together new data from some of the largest astronomical surveys across the electromagnetic spectrum, that are currently underway.