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

放大活跃星系的反馈：第一次高分辨率射电勘测

• 批准号: MR/Y020405/1
• 负责人: Leah Morabito
• 金额: $ 75.82万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FY020405%2F1
• 关键词: Zooming; feedback; active; galaxies; first

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 output 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.Observations of low-frequency radio emission are a powerful tool to pinpoint what is happening in AGN. This emission traces relativistic electrons in jets launched by a super-massive black hole and winds of outflowing material blown out into the galaxy by the super-massive black hole. However, due to their low spatial resolution, current radio surveys have difficulty distinguishing between this activity and radio emission from star formation. My FLF project overcomes this by using ultra-high spatial resolution radio observations, which rely on advanced calibration techniques I developed for the LOw Frequency ARray (LOFAR), a unique array of radio antenna stations spread across Europe. LOFAR can be a smaller or a bigger 'lens' by using only some or all of the stations: the more we use, the higher the resolution that can be achieved, but this requires specialised calibration techniques. LOFAR is unique in that it can achieve high resolution across a field of view more than 20 times larger than any other similar resolution radio telescope, which is critical to build the large samples necessary to understand AGN activity.My ongoing FLF project is to enact the first wide area, high resolution survey. I am doing this by post-processing data from the LOFAR Two-metre Sky Survey (LoTSS). The survey is recorded with all LOFAR antennas, but standard processing only uses those located in the Netherlands, providing lower resolution. Already I have demonstrated that we can make small high-resolution images (>20 times better than the standard processing) across the field of view, and guided the development of wide-field techniques that image the full field of view, although at a high computational cost.Using these exciting new images, my initial scientific results include identifying an entirely new sample of galaxies where star formation and AGN activity have been simultaneously measured using a combination of these high-resolution and standard imaging techniques; this is the largest sample of its kind by two orders of magnitude. From this, we are already learning that the AGN contribution in faint galaxies is higher than previously thought, with implications for our understanding of how galaxies form and evolve, and this project will continue to quantify this to understand the role of AGN in galaxy evolution.Conducting the first high-resolution survey across the entire Northern sky will allow me to build robust samples, the largest of their kind, 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. 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.Over the next several years, my work will lay the foundation for future scientific surveys with the SKA, in which the UK has heavily invested. I will continue to develop international collaborations with SKA pathfinder teams in South Africa, the Netherlands, and India, while placing Durham and the UK at the forefront of this exciting new revolution in science.

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什么角色呢？在大约10%的星系中，我们观察到由这些黑洞提供动力的等离子体流出和喷射等高能现象。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得知，活动星系核与其宿主星系之间的反馈会对该星系的演化产生重大影响。我们所不知道的是活动星系核反馈如何运作的细节，低频射电辐射的观测是确定活动星系核中发生了什么的有力工具。这种辐射追踪了由超大质量黑洞发射的喷流中的相对论电子，以及由超大质量黑洞吹向星系的外流物质风。然而，由于空间分辨率较低，目前的无线电测量很难区分这种活动和星星形成的无线电发射。我的FLF项目通过使用超高空间分辨率的无线电观测克服了这一点，该观测依赖于我为低频阵列（LOFAR）开发的先进校准技术，LOFAR是一个遍布欧洲的独特无线电天线站阵列。LOFAR可以是一个更小或更大的“透镜”，只使用部分或全部测站：我们使用的测站越多，可以实现的分辨率就越高，但这需要专门的校准技术。LOFAR的独特之处在于它可以在比任何其他类似分辨率射电望远镜大20倍的视场内实现高分辨率，这对于建立了解AGN活动所需的大样本至关重要。我通过对LOFAR两米巡天（LoTSS）的数据进行后处理来做到这一点。该调查是记录与所有LOFAR天线，但标准处理只使用那些位于荷兰，提供较低的分辨率。我已经证明了我们可以制作小的高分辨率图像（比标准处理好20倍以上），并指导了对全视场成像的宽视场技术的发展，尽管计算成本很高。使用这些令人兴奋的新图像，我最初的科学成果包括确定了一个全新的星系样本，其中星星的形成和活动星系核的活动是同时使用这些组合来测量的高分辨率和标准成像技术;这是同类样品中最大的两个数量级。由此，我们已经了解到活动星系核在昏暗星系中的贡献比以前认为的要高，这对我们理解星系如何形成和演化有着重要意义，这个项目将继续量化这一点，以了解活动星系核在星系演化中的作用。在整个北方天空进行第一次高分辨率调查将使我能够建立可靠的样本，这是同类样本中最大的，研究活动星系核产生射电辐射的物理过程，在大样本星系中控制这些过程的性质，以及这些过程如何通过星星形成影响星系的典型生长。我将通过我的UKRI-FLF项目推动AGN反馈研究的重大进展，并将该领域推向新的令人兴奋的领域，以回答基本的天体物理学问题。在接下来的几年里，我的工作将为英国投入巨资的SKA未来的科学调查奠定基础。我将继续与南非、荷兰和印度的SKA开拓者团队开展国际合作，同时将达勒姆和英国置于这场激动人心的新科学革命的前沿。