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的黑洞。今天最大的星系的质量是太阳的一万亿多倍，而超大质量黑洞的质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？宇宙几乎有140亿年的历史，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个时代的特点是小星系之间的猛烈碰撞。这些碰撞压缩了星系中的气体形成恒星，新恒星为超大质量黑洞提供了燃料，今天的大质量星系在其中心聚集了巨大的黑洞。尽管这张广为接受的星系形成图，我们仍然没有观察到许多这样的过程发生，特别是在100亿年前我们宇宙历史上非常活跃的增长期。我们想要捕捉最大质量的星系和超大质量黑洞，因为它们正在增长，但这些系统非常罕见；寻找它们就像大海捞针！我们不仅需要精密的望远镜，可以扫描整个天空，寻找这些怪物星系，而且它们还需要足够灵敏，能够探测到从星系最初形成到今天到达我们这里的光，这些光已经走过了数十亿年。直到最近，这才成为可能，世界上一些最大的望远镜上安装了新的数码相机，以提供覆盖大部分天空的敏感图像。我正在处理几个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，因为它们正在经历重大的增长。我已经在遥远的宇宙中发现了这些超大质量增长星系中的第一个。通过对这些新发现的星系进行高分辨率成像，我们将能够观察到它们内部发生的各种物理过程，以及超大质量黑洞是如何影响这些过程的。在我们新的天空数字图像中，潜藏着更罕见的系统，如我们宇宙中的第一个星系和超大质量黑洞，可以追溯到宇宙只有5亿年的时候。我们现在能够观察到这些星系在它们成长为今天的怪物黑洞的过程中，第一次开始为它们的超大质量黑洞提供食物。观察第一个进食阶段对于建立对超大质量黑洞如何生长的理解至关重要。大多数数字成像测量在电磁光谱的可见部分探测到来自星系的星光。然而，星系中的尘埃可以吸收可见光，然后再以更长的红外波长重新辐射。因此，红外数据可以对星系中恒星的形成提供最公正的看法。利用追踪红外波长光的新调查，我的研究将测量在遥远星系中正在形成的恒星的数量，这些星系正在活跃地供应超大质量黑洞。其目的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将变得多大。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组装时的形成，建立一幅连贯的观测图景。这将通过汇集目前正在进行的一些跨电磁频谱的最大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.