Zooming in on feedback in active galaxies: the first high-resolution radio survey

几乎每个大质量星系的中心都存在一个超大质量黑洞，但它们在星系演化中扮演着什么角色呢？在大约10%的星系中，我们观察到了由这些黑洞提供能量的等离子体流出和喷射等能量现象。当一个星系表现出这些特征时，我们称之为活动星系，并将黑洞及其能量输出称为活动星系核(AGN)。我们从观测和宇宙学模拟中都知道，活动星系核和其宿主星系之间的反馈可以对该星系的演化产生重大影响。我们不知道的是AGN反馈如何工作的细节。目前的AGN反馈研究依赖于间接证据，并侧重于单个对象或小样本。要区分恒星形成和活动星系核之间的区别是极其困难的，恒星形成是星系正常生长的方式。高分辨率成像可以有所帮助，在射电波长上，仅这一点就足以清楚地区分活动星系核活动和恒星形成。传统上，具有足够高分辨率的射电望远镜具有很小的视场，这限制了对少数星系的研究。下一代低频射电望远镜的出现为克服这一挑战提供了一种新的令人兴奋的方法。这依赖于使用我开发的技术结合低频阵列(LOFAR)的广域和高分辨率能力。LOFAR是一种平方公里阵列(SKA)探路器，天线遍布整个欧洲。默认操作只使用以荷兰为中心的天线，但我已经开发了一种高分辨率成像数据管道，将来自阵列中所有天线的信号组合在一起，提供更大的有效镜头，分辨率提高20倍。我的高分辨率工作为无线电测量开辟了一个新的制度，我保持着100 MHz以下(略低于FM无线电频段)的最高分辨率图像记录。我雄心勃勃且令人兴奋的UKRI FLF项目是在整个北方天空进行第一次高分辨率调查，这将使我能够研究活动星系核产生射电发射的物理过程，这些过程在大样本星系中是什么性质决定的，以及这些过程如何通过恒星形成影响星系的典型增长。这项调查将建立在天空有趣区域的较小数据集上，覆盖无线电、红外、光学和X射线波长，最终覆盖整个北方天空。我将通过我的UKRI-FLF项目推动活动星系核反馈研究的重大进展，并在回答基本天体物理问题方面将该领域推向新的和令人兴奋的领域。处理如此大量的数据将成为开发处理大数据的工具和技术的大趋势。我将利用跨学科科学的机会，包括与计算机科学家合作，开发新的算法，在大型调查中识别和分类来自活动星系核的无线电辐射。在接下来的几年里，我的工作将为未来与SKA进行的科学调查奠定基础，英国已经在该项目上投资了1.19亿GB。我将与南非、荷兰的SKA探路者团队建立国际合作，并将达勒姆和英国置于这场激动人心的新科学革命的前沿。

A super-massive black hole exists at the centre of almost every massive galaxy, but what role do they play in galaxy evolution? In about 10 percent of all galaxies, we observe energetic phenomena like outflows and jets of plasma that are powered by these black holes. When a galaxy shows these characteristics we call it an active galaxy, and refer to the black hole and its energetic ouput as an active galactic nucleus (AGN). We know from both observations and cosmological simulations that feedback between an AGN and its host galaxy can have a significant impact on that galaxy's evolution. What we do not know are the details of how this AGN feedback works. Current AGN feedback studies rely on indirect evidence and focus on individual objects or small samples. It can be extremely difficult to tell the difference between star formation, which is how galaxies normally grow, and AGN activity. High resolution imaging can help, and at radio wavelengths this alone is enough to clearly distinguish between AGN activity and star formation. Traditionally radio telescopes with high enough resolution to do this have tiny fields of view which limits studies to small numbers of galaxies. The advent of next-generation of low-frequency radio telescopes offers a new and exciting way to overcome this challenge. This relies on combining both wide-field and high-resolution capabilities of the LOw Frequency ARray (LOFAR), using techniques I have developed. LOFAR is a Square Kilometre Array (SKA) pathfinder with antennas spread all across Europe. Default operations use only the antennas centred in the Netherlands, but I have developed a high-resolution imaging data pipeline to combine signals from all the antennas in the array, providing a larger effective 'lens' and 20 times improved resolution. My high-resolution work is opening a new regime for radio surveys, and I hold the record for the highest resolution image ever made below 100 MHz (just below the FM radio band). My ambitious and exciting UKRI FLF project is to conduct the first high-resolution survey across the entire Northern sky, which will allow me to study the physical processes by which AGN produce radio emission, what properties govern these processes across large samples of galaxies, and how these processes impact the typical growth of galaxies through star formation. This survey will build from smaller datasets on interesting areas of sky with exquisite coverage across radio, infrared, optical, and X-ray wavelengths, and eventually cover the entire Northern sky. I will drive forward major advances in AGN feedback studies with my UKRI-FLF project, and push the field to new and exciting territory in answering fundamental astrophysical questions. Dealing with such large data volumes will feed into the general trend for developing tools and techniques to deal with Big Data. I will exploit opportunities for interdisciplinary science, including working with computer scientists to develop new algorithms for identifying and classifying the radio emission from AGN in large surveys. In the next few years, my work will lay the foundation for future scientific surveys with the SKA, in which the UK has already invested £119 million. I will build international collaborations with SKA pathfinder teams in South Africa, the Netherlands, and place Durham and the UK at the forefront of this exciting new revolution in science.