Galaxy-scale jets with new extragalactic radio surveys

来自超大质量黑洞的河外喷流在星系演化过程中扮演着重要的角色。在过去的十年里，这一领域的研究主要集中在丰富的星系团中心的强大喷流上，在那里，喷流似乎调节着大质量星系中的恒星形成——这一过程现在被纳入了大多数星系形成的宇宙学模拟中。但是，包含在其宿主星系内的较小的喷流也可以对单个星系的规模产生强大的影响，正如我们从最近测量其冲击影响的x射线研究中发现的那样（例如，Croston et al. 2007, 2009, Mingo et al. 2011, 2012, Heesen et al. 2014）。它们的低射电亮度和小尺寸意味着这些喷流在以前的射电调查中很难识别。由于这个原因，人口的统计数据以及这些小规模喷流在高红移宇宙中的作用尚不清楚。同样，通过x射线追踪直接测量它们的影响也只能对少数物体进行测量。该项目将涉及利用LOFAR（低频阵列）对河外天空进行新的低频调查，LOFAR具有识别和表征星系尺度喷流的灵敏度、分辨率和图像保真度。通过将这一群体与其他波长的数据交叉匹配，将有可能回答有关它们有多普遍的问题，以及它们的无线电特性与黑洞质量、吸积行为和环境之间的关系。也有可能进行新的和存档的x射线观测，以测量单个物体的激波特性。

Extragalactic jets from supermassive black holes are known to play an important role in the process of how galaxies evolve. Research in this area over the last decade has focused particularly on powerful jets in the centres of rich galaxy clusters, where jets appear to regulate star formation in massive galaxies - a process now incorporated into most cosmological simulations of galaxy formation. But smaller jets contained within their host galaxies can also have a powerful effect on the scale of individual galaxies, as we have found from recent X-ray studies measuring the impact of their shocks (e.g. Croston et al. 2007, 2009, Mingo et al. 2011, 2012, Heesen et al. 2014). Their low radio luminosity and small size mean that these jets have been difficult to identify in previous radio surveys. For this reason, the demographics of the population, and the role of these small-scale jets in the high-redshift Universe, are not understood. Similarly, direct measurements of their impact via X-ray follow up have only been possible for a handful of objects.This project will involve exploiting new low-frequency surveys of the extragalactic sky with LOFAR (the Low-Frequency Array), which have the sensitivity, resolution and image fidelity to identify and characterize galaxy-scale jets. By cross-matching this population with data at other wavelengths, it will be possible to answer questions about how common they are, and how their radio properties relate to their black hole mass, accretion behaviour and environment. There is also the possibility to work on new and archival X-ray observations to measure shock properties in individual objects.