LOFAR observations of SZ-selected galaxy clusters, and high-fidelity imaging

SZ 选定星系团的 LOFAR 观测和高保真成像

• 批准号: 159479748
• 负责人: Professor Dr. Marcus Brüggen, Ph.D.
• 金额: --
• 依托单位: Max-Planck-Institut für Astrophysik (MPA)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/159479748?language=en
• 关键词: LOFAR; observations; SZ; selected; galaxy

Giant radio halos in galaxy clusters provide the best evidence for the existence of a relativistic plasma (particles and magnetic fields) in the intergalactic medium (IGM). The nature of these Mpc-sized, steep spectrum synchrotron sources that are not clearly associated with individual galaxies, is not yet known. In this project, we pursue a two-pronged approach.In the first sub-project, we aim to investigate whether such halos are a common phenomenon in galaxy clusters and whether their radio power is related to their mass. The predominant baryonic component, namely the hot gas, can be traced both, in X-rays as well as via the Sunyaev-Zel'dovich (SZ) effect. The X-ray emission of clusters is mapped in various surveys conducted with XMM and Chandra and will also be a prime goal of the upcoming eRosita mission. The SZ signal has been measured for a large cluster sample and compiled in the Planck All-Sky Cluster Catalog. A large sample of galaxy clusters will be observed in the framework of the Tier 1 Survey, a complete survey of the northern sky to be conducted with the new LOFAR radio telescope. This systematic low-frequency survey of galaxy clusters at the lowest radio frequencies will remedy what has been a major obstacle in comparing the thermal and non-thermal components in galaxy clusters: the lack of a homogeneous low-frequency data set that can map the population of non-thermal electrons in a large sample of clusters to unprecedented depth. The radio maps can be compared directly to the X-ray and SZ data that yield the pressures, densities and temperatures of the thermal component. Finally, the technique of three-dimensional "Faraday Synthesis", developed in the framework of our Research Unit (Project A 8), will help to investigate the magnetic-field structure in cluster radio halos and shed light of their low degrees of linear polarization. The thus measured relationship between the radio emission, the magnetic field structure as well as the density distribution of the thermal gas, will give essential clues to the origin of radio halos.In a second sub-project, we strive to establish tools that will finally facilitate the discrimination between many of the models for cluster halos and relics, which is hampered by the many observational artefacts of radio maps. The aim is to produce high-fidelity radio maps of a number of prominent galaxy clusters using existing archival data and complement them with any new data from LOFAR (and other telescopes). These cutting-edge quality maps are to be combined into intensity, spectral index and spectral curvature maps using multi-frequency imaging methods. In addition, we will process polarimetric data of the selected galaxy clusters, making use of novel methods: RM Synthesis yields spectral data cubes containing three-dimensional information about the magnetic field, and Faraday Synthesis, which combines Aperture and RM Synthesis in a single three dimensional Faraday cube reconstruction step. With these tools at hand, one can overcome Faraday depolarization effects which erase the intrinsic polarization of the synchrotron emission of cluster radio haloes.

星系团中的巨型射电晕为星系际介质（IGM）中存在相对论性等离子体（粒子和磁场）提供了最好的证据。这些百万pc大小的陡谱同步辐射源的性质还不清楚，与个别星系没有明显的联系，目前还不清楚。在这个项目中，我们采取双管齐下的方法。在第一个子项目中，我们的目标是调查这种晕是否是星系团中的常见现象，以及它们的射电功率是否与它们的质量有关。主要的重子成分，即热气体，可以通过X射线和Sunyaev-Zel'dovich（SZ）效应来追踪。星团的X射线发射在XMM和钱德拉进行的各种调查中被绘制出来，也将是即将到来的eRosita使命的主要目标。SZ信号已被测量的一个大的集群样本，并编制在普朗克全天星团目录。将在第一级巡天的框架内对星系团的大量样本进行观测，第一级巡天是用新的LOFAR射电望远镜对北方天空进行的一次全面巡天。这种以最低无线电频率对星系团进行的系统性低频调查将弥补在比较星系团中的热和非热成分方面的一个主要障碍：缺乏一个均匀的低频数据集，可以将大样本星系团中的非热电子总数映射到前所未有的深度。无线电地图可以直接与X射线和SZ数据进行比较，从而产生热分量的压力，密度和温度。最后，三维“法拉第合成”的技术，在我们的研究单位（项目A8）的框架内发展，将有助于调查集群无线电晕的磁场结构和揭示其低程度的线偏振。由此测得的射电辐射、磁场结构以及热气体密度分布之间的关系将为射电晕的起源提供重要线索。在第二个子项目中，我们努力建立工具，最终将有助于区分许多星团晕和遗迹的模型，这受到许多射电图观测伪像的阻碍。其目的是利用现有的档案数据制作一些突出星系团的高保真无线电地图，并利用LOFAR（和其他望远镜）的任何新数据对其进行补充。这些高质量的地图将使用多频率成像方法合并成强度、光谱指数和光谱曲率地图。此外，我们将处理选定的星系团的偏振数据，利用新的方法：RM合成产生包含三维磁场信息的光谱数据立方体，和法拉第合成，它结合了孔径和RM合成在一个单一的三维法拉第立方体重建步骤。有了这些工具，我们可以克服法拉第去极化效应，消除集群无线电晕的同步辐射的固有偏振。

项目成果

A giant radio halo in the cool core cluster CL1821+643

• DOI: 10.1093/mnrasl/slu110
• 发表时间: 2014-07
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: A. Bonafede;H. Intema;M. Brüggen;H. Russell;G. Ogrean;K. Basu;M. Sommer;R. V. Weeren;R. Cassano;A. Fabian;H. Röttgering

A shock front at the radio relic of Abell 2744

阿贝尔 2744 号无线电遗迹的激波前沿

• DOI: 10.1093/mnras/stw1435
• 发表时间: 2016
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Eckert;Jauzac
• 通讯作者: Jauzac

Diffuse radio emission in the complex merging galaxy cluster Abell2069

• DOI: 10.1051/0004-6361/201424828
• 发表时间: 2014-12
• 期刊: Astronomy and Astrophysics
• 影响因子: 6.5
• 作者: A. Drabent;M. Hoeft;R. Pizzo;A. Bonafede;R. Weeren;U. Klein

Radio haloes in Sunyaev–Zel'dovich-selected clusters of galaxies: the making of a halo?

• DOI: 10.1093/mnras/stv2065
• 发表时间: 2015-09
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: A. Bonafede;H. Intema;M. Brüggen;F. Vazza;K. Basu;M. Sommer;H. Ebeling;F. Gasperin;H. Röttgering;R. Weeren;R. Cassano

Evidence for a pressure discontinuity at the position of the Coma relic from Planck Sunyaev-Zel'dovich effect data

• DOI: 10.1093/mnras/stu2750
• 发表时间: 2014-11
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: J. Erler;K. Basu;M. Trasatti;U. Klein;F. Bertoldi