AGN-environment interplay observed at ultra-low radio frequencies

在超低无线电频率下观察到的 AGN 环境相互作用

• 批准号: 427771150
• 负责人: Professor Dr. Marcus Brüggen, Ph.D., since 1/2022
• 金额: --
• 依托单位: Hamburger Sternwarte
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427771150?language=en
• 关键词: AGN; environment; interplay; observed; ultra

It is well known that active galactic nuclei (AGN) can influence the surrounding environment by releasing a large quantity of energy. Their action affects a wide range of scales, so that even the cosmological evolution of galaxy clusters is influenced by AGN feedback. While the scientific community has recognised long time ago that AGN effect is a crucial piece of the puzzle for galaxy and galaxy cluster evolution, the interplay between AGN activity and the surrounding environment is complex and the long-term effect of this interaction is difficult to constrain observationally. AGN feedback is mediated by jets of magnetised plasma that transport energy away from the central engine. Tracing observationally the ejected plasma is crucial to measure (i) the effect of the AGN on the environment and (ii) how the environment shapes the properties of the plasma from AGN. Fortunately, relativistic cosmic ray (CR) electrons present in these plasmas radiate in the radio band. The lower the energy of the electrons, the lower the frequency of this radio synchrotron emission. Here we aim to chart the spatial and energetic distribution of CR of AGN origin through ultra-low frequency radio observations. Thus, we will be able to look at the long-term (hundreds of Myr) interplay between AGN and the surrounding medium. Historically, deep and high-resolution observations at radio frequencies were only possible at GHz frequencies. With the advent of novel facilities, such as the Low Frequency Array (LOFAR),the window of low- (<1 GHz) and even ultra-low- (<100 MHz) radio frequencies is now ready to be explored.

活动星系核（AGN）释放出大量的能量，对周围环境产生影响。活动星系核的作用影响着广泛的尺度，因此，甚至星系团的宇宙演化也受到活动星系核反馈的影响。虽然科学界很早就认识到活动星系核效应是星系和星系团演化的关键，但活动星系核活动与周围环境之间的相互作用是复杂的，这种相互作用的长期影响很难在观测上加以限制。活动星系核的反馈是由磁化等离子体射流介导的，这些射流将能量从中央引擎传输出去。在观测上追踪活动星系核喷射出的等离子体对于测量活动星系核对环境的影响以及环境如何塑造活动星系核等离子体的性质是至关重要的。幸运的是，存在于这些等离子体中的相对论宇宙射线（CR）电子在无线电波段辐射。电子的能量越低，这种无线电同步辐射的频率就越低。在这里，我们的目标是通过超低频射电观测绘制的空间和能量分布的活动星系核起源的CR。因此，我们将能够看到活动星系核和周围介质之间的长期（数百万年）相互作用。从历史上看，只有在GHz频率下才有可能在无线电频率下进行深度和高分辨率观测。随着新设施的出现，如低频阵列（LOFAR），现在可以探索低（<1 GHz）甚至超低（<100 MHz）无线电频率的窗口。