Discovery of a $z \sim 0.8$ Ultra Steep Spectrum Radio Halo in the MeerKAT-South Pole Telescope Survey
Isaac S. Magolego, Roger P. Deane, Kshitij Thorat, Ian Heywood, William Rasakanya, Manuel Aravena, Lindsey E. Bleem, Maria G. Campitiello, Kedar A. Phadke, Just… 展开作者
Isaac S. Magolego, Roger P. Deane, Kshitij Thorat, Ian Heywood, William Rasakanya, Manuel Aravena, Lindsey E. Bleem, Maria G. Campitiello, Kedar A. Phadke, Justin Spilker, Joaquin D. Vieira, Dazhi Zhou, Bradford A. Benson, Scott Chapman, Ana Posses, Tim Schrabback, Anthony Stark, David Vizgan
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8 pages, 4 figures, 2 tables. Submitted to MNRAS Letters
Radio halos are diffuse synchrotron sources that trace the turbulent intracluster medium (ICM) of galaxy clusters. However, their origin remains unknown. Two main formation models have been proposed: the hadronic model, in which relativistic electrons are continuously injected by cosmic-ray protons; and the leptonic turbulent re-acceleration model, where cluster mergers re-energise electrons in situ. A key discriminant between the two models would be the existence of ultra-steep spectrum radio halos (USSRHs), which can only be produced through turbulent re-acceleration. Here we report the discovery of an USSRH in the galaxy cluster SPT-CLJ2337$-$5942 at redshift $z = 0.78$ in the MeerKAT-South Pole Telescope 100 deg$^2$ survey. This discovery is noteworthy for two primary reasons: it is the highest redshift USSRH system to date; and the close correspondence of the radio emission with the thermal ICM as traced by $\mathit{Chandra}$ X-ray observations, further supporting the leptonic re-acceleration model. The halo is under-luminous for its mass, consistent with a minor merger origin, which produces steep-spectrum, lower luminosity halos. This result demonstrates the power of wide-field, high-fidelity, $\lesssim1$ GHz surveys like the MeerKAT-SPT 100 deg$^2$ programme to probe the origin and evolution of radio halos over cosmic time, ahead of the Square Kilometre Array.
We aim to carry out a radio study of the SoUthern Cluster sCale Extended Source Survey (SUCCESS) sample consisting of twenty massive (M$_{500} > 5\times10^{14}$ M$_{\odot}$), nearby (redshift $<0.3$) and southern ($-50^{\circ} < δ< -30^\circ$) galaxy clusters detected by the Planck satellite and the South Pole Telescope. Here we report targeted GMRT observations (325/610 MHz) for a sub-sample of nine clusters. We also use the first data release of MeerKAT Galaxy Cluster Legacy Survey (1283 MHz) for five of these nine clusters. The properties of the mini-halo in RXC J0528.9-3927, a candidate mi…
We explore the possibility of performing an HI intensity mapping survey with the South African MeerKAT radio telescope, which is a precursor to the Square Kilometre Array (SKA). We propose to use cross-correlations between the MeerKAT intensity mapping survey and optical galaxy surveys, in order to mitigate systematic effects and produce robust cosmological measurements. Our forecasts show that precise measurements of the HI signal can be made in the near future. These can be used to constrain HI and cosmological parameters across a wide range of redshift.
Looking At the Distant Universe with the MeerKAT Array (LADUMA)
MeerKAT（64 x 13.5米碟形射电干涉仪）是南非平方公里阵列（SKA）的先驱仪器，探索碟形天线设计，仪器和卡鲁沙漠站点的特征，预计将于2016年在天空中出现。两个最高优先级之一，重点项目是一个单一的深场，总集成时间为5000小时，目的是通过其21厘米线发射来检测中性原子氢，以达到红移单位及更高。这是第一次真正深入的HI调查，将有助于限制星系组装和演化的燃料模型。它将测量宇宙中性气体密度的演变及其在星系中的分布，探索星系中气体的演变，测量塔利-费舍尔关系，测量OH脉泽计数，并解决更多的问题。在这里，我们提出了观测策略和设想的科学情况下，这个独特的深场，其中包括钱德拉深场南（和足迹的GOODS，GEMS和其他几个调查），以产生一个单一的遗产多波长数据集。
A "MeerKAT-meets-LOFAR" Study of 2A 0335+096: Discovery of a Complex 500 kpc Radio Halo in a Disturbed Cool-Core Cluster
Astronomisches Institut der Ruhr-Universität Bochum（波鸿鲁尔大学天文研究所）；Ruhr Astroparticle and Plasma Physics Center（鲁尔天体粒子与等离子体物理中心）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；INAF – IASF Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano（意大利国家天体物理研究所-米兰空间天体物理学和宇宙物理学研究所）；Institute for Computational Cosmology, Department of Physics, Durham University（杜伦大学物理系计算宇宙学研究所）；INAF – Istituto di Radioastronomia（意大利国家天体物理研究所-射电天文学研究所）；Dipartimento di Fisica e Astronomia, Università di Bologna（博洛尼亚大学物理与天文学系）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Thuringer Landessternwarte（图林根州立天文台）
MeerKAT observations of Abell 1775 and Abell 1795: the discovery of a hadronic radio halo?
Leiden University（莱顿大学）；University of Toronto（多伦多大学）；INAF – Istituto di Radioastronomia（意大利国家天体物理研究所射电天文学研究所）；Ruhr-Universität Bochum（波鸿鲁尔大学）；Durham University（杜伦大学）；Università di Bologna（博洛尼亚大学）；University of Hamburg（汉堡大学）
HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey $-$ I. Probing the richness of the Great Attractor Wall across the inner Zone of Avoidance
The plethora of diffuse emission in Abell 2034 as revealed by MeerKAT polarization observations
Università di Bologna（博洛尼亚大学）；IRA INAF（INAF天文研究所）；INAF - IASF Milano（INAF米兰天体物理研究所）；Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；AIM（天体物理学和宇宙学研究所）；Minnesota Institute for Astrophysics, University of Minnesota（明尼苏达大学天体物理研究所）；Astronomisches Institut der Ruhr-Universität Bochum (AIRUB)（鲁尔大学波鸿天体物理研究所）；Ruhr Astroparticle and Plasma Physics Center (RAPP Center)（鲁尔高能粒子与等离子体物理中心）；Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University（罗德斯大学物理与电子学院射电天文技术与理论中心）；South African Radio Astronomy Observatory（南非射电天文观测台）
The nature of the time correlated noise component (the 1/f noise) of single dish radio telescopes is critical to the detectability of the HI signal in intensity mapping experiments. In this paper, we present the 1/f noise properties of the MeerKAT receiver system using South Celestial Pole (SCP) tracking data. We estimate both the temporal power spectrum density and the 2D power spectrum density for each of the antennas and polarizations. We apply Singular Value Decomposition (SVD) to the dataset and show that, by removing the strongest components, the 1/f noise can be drastically reduced, ind…
Abell 754 is a rich galaxy cluster at $z=0.0543$ and is considered the prototype of a major cluster merger. Like many dynamically unrelaxed systems, it hosts diffuse radio emission on Mpc-scales. Extended synchrotron sources in the intra-cluster medium (ICM) are commonly interpreted as evidence that a fraction of the gravitational energy released during cluster mergers is dissipated into nonthermal components. Here, we use new MeerKAT UHF- and L-band observations to study nonthermal phenomena in Abell 754. These data are complemented with archival XMM-Newton observations to investigate the res…
During their lifetime, galaxy clusters grow through the accretion of matter from the filaments of the large scale structure and from mergers with other clusters. These mergers release a large amount of energy into the intracluster medium (ICM) through merger shocks and turbulence. These phenomena are associated with the formation of radio sources known as radio relics and radio halos, respectively. Radio relics and halos are unique proxies to study the complex properties of these dynamically active regions of clusters and in general the micro physics of the ICM. Abell 3667 is a spectacular exa…
Cosmic dance in the Shapley Concentration Core II. The uGMRT-MeerKAT view of filaments in the brightest cluster galaxies and tailed radio galaxies in the A3528 cluster complex
本文利用 uGMRT 和 MeerKAT 射电观测结合 eROSITA X 射线数据，研究沙普利超星系团核心 A3528 复合体，发现最亮团星系周围存在谱指数极陡的弥散射电纤维，并提出小型并合可重新加速射电星系等离子体。
Extended radio emission in and around the merging cluster A520 as seen by MeerKAT
U.S. Naval Research Laboratory（美国海军研究实验室）；National Radio Astronomy Observatory（国家射电天文台）；South African Radio Astronomy Observatory（南非射电天文台）；NASA/Goddard Space Flight Center（NASA/戈达德太空飞行中心）；INAF - Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；Università di Roma Tor Vergata（罗马托维加塔大学）；INFN, Sezione di Roma 2, Università di Roma Tor Vergata（意大利国家核物理研究所罗马第二分部，罗马托维加塔大学）
The MeerKAT Fornax Survey VII. Characterisation of the Fornax cluster's magnetic field and new insights on magnetisation in large scale systems
INAF - Osservatorio Astronomico di Cagliari（意大利国家天体物理研究所卡利亚里天文台）；Wits Centre for Astrophysics, School of Physics, University of the Witwatersrand（威特沃特斯兰德大学物理学院天体物理中心）；Ruhr University Bochum（鲁尔大学波鸿分校）；Netherlands Institute for Radio Astronomy (ASTRON)（荷兰射电天文研究所）
We present a radio and X-ray analysis of the galaxy cluster SPT-CL J2032-5627. Investigation of public data from the Australian Square Kilometre Array Pathfinder (ASKAP) at 943 MHz shows two previously undetected radio relics at either side of the cluster. For both relic sources we utilise archival Australia Telescope Compact Array (ATCA) data at 5.5 GHz in conjunction with the new ASKAP data to determine that both have steep integrated radio spectra ($α_\mathrm{SE} = -1.52 \pm 0.10$ and $α_\mathrm{NW,full} = -1.18 \pm 0.10$ for the southeast and northwest relic sources, respectively). No shoc…
We report on the discovery of a mysterious ultra-steep spectrum (USS) synchrotron source in the galaxy cluster Abell 2877. We have observed the source with the Murchison Widefield Array at five frequencies across 72-231 MHz and have found the source to exhibit strong spectral curvature over this range as well the steepest known spectra of a synchrotron cluster source, with a spectral index across the central three frequency bands of $α= -5.97^{+0.40}_{-0.48}$. Higher frequency radio observations, including a deep observation with the Australia Telescope Compact Array, fail to detect any of the…
Discovery of a nearby radio relic in the low-mass, merging cluster Abell 4067
University of the Witwatersrand（威特沃特斯兰德大学）；University of Pretoria（比勒陀利亚大学）；SKA Observatory（平方公里阵列射电望远镜天文台）；University of Oxford（牛津大学）；Rhodes University（罗兹大学）；South African Radio Astronomy Observatory（南非射电天文观测站）；Texas A&M University（德克萨斯农工大学）；Chulalongkorn University（朱拉隆功大学）
We present new low-frequency ($ν= 88$-216 MHz) observations of the complex merging galaxy cluster Abell 3266. These new observations are taken with the Murchison Widefield Array (MWA) in its Phase II 'extended', long-baseline configuration, offering the highest-resolution low-frequency view of the cluster to date. We report on the detection of four steep spectrum ($α\lesssim -1$ for $S_ν\propto ν^α$) extended radio sources within the cluster. We confirm the detection of a $\sim 570$ kpc radio relic to the south of the cluster, and a possible bridge of emission connecting the relic to the clust…
Galaxy clusters have been found to host a range of diffuse, non-thermal emission components, generally with steep, power law spectra. In this work we report on the detection and follow-up of radio halos, relics, remnant radio galaxies, and other fossil radio plasmas in Southern Sky galaxy clusters using the Murchison Widefield Array and the Australian Square Kilometre Array Pathfinder. We make use of the frequency coverage between the two radio interferometers - from 88 to $\sim 900$ MHz - to characterise the integrated spectra of these sources within this frequency range. Highlights from the …
Radio halos and relics are Mpc-scale diffuse radio sources in galaxy clusters, with a steep spectral index $α>1$ ($S\propto ν^{-α}$). It has been proposed that they arise from particle acceleration induced by turbulence and weak shocks, injected in the intracluster medium (ICM) during mergers. MACS J1149.5+2223 (MACS J1149) is a high redshift ($z=0.544$) galaxy cluster possibly hosting a radio halo and a relic. We analysed LOFAR, GMRT, and JVLA radio data at 144, 323, 1500 MHz, and Chandra X-ray data to characterise the thermal and non-thermal properties of the cluster. We obtained radio image…
Extended, steep, and ultra-steep spectrum radio emission in a galaxy cluster is usually associated with recent mergers. Simulations show that radio phoenixes are aged radio galaxy lobes whose emission reactivates when a low Mach shock compresses it. A85 hosts a textbook example of a radio phoenix at about 320 kpc southwest of the cluster center. We present a new high resolution 325 MHz GMRT radio map illustrating this radio phoenix's complex and filamentary structure. The full extent of the radio structure is revealed for the first time from these radio images of A85. Using archival \textit{Ch…
