Supermassive black hole growth - a small-scale solution to a large-scale problem

几乎每个星系的中心都有一个暗天体，其质量超过太阳的一百万倍。虽然质量很大，但这些物体已经被自己的引力压缩到极高的密度，以至于光无法逃离它们的表面;这些是超大质量黑洞（SMBH）。这些奇异的天体是如何形成的是天文学家面临的一个突出的谜团，也是我发现的一个特别有趣的谜团。通过远距离观测，我们能够瞥见宇宙生命最初几十亿年发生的事情。虽然很难在这些距离上进行研究，但可以对一些SMBH进行“称重”。令人惊讶的是，这表明它们在宇宙只有~ 10亿岁时就已经完全长大了。尽管科学家们认为增长应该需要很长时间，但这一发现要求它们以惊人的速度增长，因为物质以极端的速度落在黑洞上-比辐射和引力平衡所允许的速度更快，即所谓的爱丁顿极限。吸积是如何以这样的速度运行的还不清楚，但这是天体物理学中一个紧迫的问题--我打算解决这个问题。虽然我们不能直接研究SMBH的生长，但我们可以观察到物质是如何落在附近星系的SMBH上，以及落在我们银河系内小得多的黑洞（在双星系统中有轨道恒星：BHB）上的。因此，我们知道物质不会直接落在黑洞上，而是形成了一个吸积盘，释放出大量的辐射。在非常高的速率下，并不是所有的物质福尔斯都落在黑洞上，而是有一部分以“风”或“喷流”的形式被排出。风以相当“慢”的速度（约为光速的10%）从圆盘表面携带物质，而喷流则是以接近光速的速度从黑洞附近喷射物质的更强大的喷射。这是合乎逻辑的，类似的流出将伴随着SMBH的增长，与物质从吸积流和重新分配到周围的环境-一种形式的“反馈”。了解爱丁顿吸积和相关的流出的性质是必要的理解SMBH的增长和影响反馈必须有对宿主星系。在实践中，这需要观察吸积流在达到爱丁顿极限时如何变化，并与流出耦合，即它们如何相互作用。在实践中，这被证明是非常困难的：从吸积流到附近星系的SMBH和银河系BHB上的发射被中间物质所掩盖，阻止了耦合的观察。我的建议以一种新的方式解决这个问题：通过观察在附近星系中以高速率吸积的BHB，其中干预物质的量要低得多，从而可以研究流入的发射。这些河外BHB有两种“风格”：那些在银河系中常见并显示出强大的喷流，以及那些更明亮并被认为是具有强风的爱丁顿吸积的更极端形式。我正在领导对两个邻近星系中具有强大喷流的新BHB的首次主要搜索。通过使用多种波长范围内的仪器进行观察，包括世界上最重要的射电望远镜VLA和NASA的X射线卫星Swift，我将观察圆盘和射流如何一起变化，从而限制流入的性质和射流如何发射。为了理解强风中最亮的光源，我将把联合收割机新颖的分析技术与理论结合起来，揭示流入和流出的本质。通过研究本地宇宙中SMBH的吸积，我将把我的发现外推到更大的黑洞质量，那里的流入和流出的耦合无法研究。最后，通过模拟高红移SMBH的增长，我将能够探索反馈对宿主星系的影响，在一个时代，否则隐藏的视图。

In the centre of almost every galaxy sits a dark object, with a mass over a million times that of the Sun. Although massive, these objects have been compressed by their own gravity to extremely high densities, so dense in-fact that light cannot escape their surface; these are the supermassive black holes (SMBHs). How these exotic objects formed is one of the outstanding mysteries facing astronomers and one I find particularly intriguing.By looking to great distances we are able to glimpse what happened in the first few billion years of the Universe's life. Although very difficult to perform studies at these distances, a few SMBHs can be 'weighed'. Surprisingly this has shown that they were fully-grown when the Universe was only ~1 billion years old. Although scientists thought that growth should take a long time, this discovery demands that they instead grew incredibly quickly by material falling onto the black hole at extreme rates - faster than should be allowed by the balance of radiation and gravity, the so-called Eddington limit. How accretion operates at such rates is unclear but is a pressing issue in astrophysics - an issue I aim to address.Although we cannot study the SMBHs growing directly, we can observe how material falls onto SMBHs in nearby galaxies and onto much smaller black holes (with orbiting stars in binary systems: BHBs) within our own Galaxy. As a result, we know that material doesn't fall directly onto the black hole but forms an accretion disc, which emits large amounts of radiation. At very high rates, not all of the material falls onto the black hole; instead some fraction is expelled in 'winds' or 'jets'. Winds carry material from the surface of the disc at fairly 'slow' speeds (~10% of the speed of light) whereas jets are much more powerful ejections of matter from close to the black hole at almost the speed of light. It is logical that similar outflows will have accompanied the SMBH growth, with matter taken from the accretion flow and redistributed to the surroundings - a form of 'feedback'.Understanding the nature of Eddington accretion and the associated outflows is necessary for understanding the growth of SMBHs and the impact feedback must have had on the host galaxy. In practice this requires observing how the accretion flow changes as it reaches the Eddington limit and couples to the outflow, i.e. how they interact. In practice this has proven to be extremely difficult: emission from the accretion flow onto both SMBHs in nearby galaxies and onto Galactic BHBs is obscured by intervening material, preventing a view of the coupling. My proposal approaches this problem in a new way: by looking at BHBs accreting at high rates in nearby galaxies where the amount of intervening material is much lower, allowing the emission from the inflow to be studied. These extragalactic BHBs come in two 'flavours': those which are commonly seen in the Milky Way and show powerful jets, and those which are even brighter and thought to be a more extreme form of Eddington accretion with powerful winds. I am leading the first major search for new BHBs with powerful jets in two nearby galaxies. By observing with several instruments across a range of wavelengths, including the world's foremost radio telescope, the VLA, and NASA's X-ray satellite, Swift, I will observe how the disc and jets change together, thereby constraining both the nature of the inflow and how the jets are launched. In order to understand the brightest sources with powerful winds, I will combine novel analysis techniques with theory to reveal the nature of both inflow and outflow. By studying accretion onto SMBHs in the local Universe, I will extrapolate my findings to larger black hole masses where the coupling of inflow and outflow cannot be studied. Finally, by using simulations of high redshift SMBH growth I will be able to explore the impact of feedback on the host galaxies, in an epoch otherwise hidden from view.