scholarly journals Diffuse radio sources in clusters of galaxies: models and long-wavelength radio observations

2006 ◽  
Vol 2 (14) ◽  
pp. 369-371
Author(s):  
Craig L. Sarazin
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Radio Observations ◽  
Hadronic Interactions ◽  
Long Wavelength ◽  
Cluster Environment ◽  
Cluster Mergers ◽  
Radio Halos

AbstractClusters of galaxies contain several types of diffuse radio sources with very steep radio spectra which are associated with the cluster environment, including central radio bubbles, cluster radio relics, and cluster radio halos. Radio halos and relics are found only in merging clusters. Cluster radio relics may be produced by particle acceleration in merger shocks, while radio halos, may result from electron re-acceleration by turbulence produced by mergers. Secondary production of electrons and positrons by hadronic interactions also plays a role. If cluster radio halos and relics are related to mergers, then deep low frequency radio surveys could detect 1000's of clusters. Long-wavelength radio observations have a great potential to help us understand clusters and large scale structure, and can provide a diagnostic of cluster mergers, which affect the use of clusters in cosmological and dark energy studies.

scholarly journals LOFAR observations of the XMM-LSS field

2019 ◽  
Vol 622 ◽  
pp. A4 ◽  
Author(s):  
C. L. Hale ◽  
W. Williams ◽  
M. J. Jarvis ◽  
M. J. Hardcastle ◽  
L. K. Morabito ◽  
...  
Keyword(s):  
Large Scale ◽  
Angular Resolution ◽  
Low Frequency ◽  
Primary Beam ◽  
Electromagnetic Spectrum ◽  
Radio Sources ◽  
Spectral Indices ◽  
The North ◽  
True Source ◽  
Scale Calibration

We present observations of the XMM Large-Scale Structure (XMM-LSS) field observed with the LOw Frequency ARray (LOFAR) at 120–168 MHz. Centred at a J2000 declination of −4.5°, this is a challenging field to observe with LOFAR because of its low elevation with respect to the array. The low elevation of this field reduces the effective collecting area of the telescope, thereby reducing sensitivity. This low elevation also causes the primary beam to be elongated in the north-south direction, which can introduce side lobes in the synthesised beam in this direction. However the XMM-LSS field is a key field to study because of the wealth of ancillary information, encompassing most of the electromagnetic spectrum. The field was observed for a total of 12 h from three four-hour LOFAR tracks using the Dutch array. The final image presented encompasses ∼27 deg2, which is the region of the observations with a >50% primary beam response. Once combined, the observations reach a central rms of 280μJy beam−1at 144 MHz and have an angular resolution of 7.5 × 8.5″. We present our catalogue of detected sources and investigate how our observations compare to previous radio observations. This includes investigating the flux scale calibration of these observations compared to previous measurements, the implied spectral indices of the sources, the observed source counts and corrections to obtain the true source counts, and finally the clustering of the observed radio sources.

scholarly journals Radio Halos in Merging Clusters

2002 ◽  
Vol 12 ◽  
pp. 513-515 ◽  
Author(s):  
Gabriele Giovannini ◽  
Luigina Feretti
Keyword(s):  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Diffuse Source ◽  
X Ray ◽  
Diffuse Sources ◽  
Physical Conditions ◽  
Show Evidence ◽  
Radio Halos

AbstractThe number of known diffuse radio sources in clusters of galaxies (halos and relics) has grown in recent years, making it possible to derive statistical considerations on the physical conditions of these sources and on the properties of related clusters. We will discuss the percentage of clusters with a diffuse source and will show evidence that diffuse sources are associated with X-ray luminous clusters which have undergone recent merger processes.

Radio Data on Clusters of Galaxies from the Culgoora Circular Array

1983 ◽  
Vol 5 (1) ◽  
pp. 114-129 ◽  
Author(s):  
O. B. Slee ◽  
Betty C. Siegman
Keyword(s):  
Low Frequency ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Circular Array ◽  
Radio Data ◽  
Contour Maps ◽  
Flux Data ◽  
Intensity Measurements ◽  
Half Power ◽  
Selection Of

The Culgoora circular array (CCA) is a 3-km-diameter ring of 96 reflectors operating at 80, 160 and 327 MHz. It has an effective collecting area of ~ 6000 m2 and achieves angular resolutions (full half-power beamwidths) of 3’.70, 1 ‘.85 and 0’.92 at the three operating frequencies. During the interval 1978-1981 we have used the CCA to make 80 and 160 MHz measurements of a comprehensive selection of radio sources which were detected during various complete surveys of clusters of galaxies (see Table 1). We have combined our low-frequency intensity measurements with other available higher-frequency flux data to compute accurate radio spectra. The 160 MHz contour maps for many of the cluster fields were used to find positions and angular sizes for the associated radio sources.

scholarly journals A GMRT Narrowband vs. Wideband Analysis of the ACT-CL J0034.40225 Field Selected from the ACTPol Cluster Sample+

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 117
Author(s):  
Sinenhlanhla P. Sikhosana ◽  
Kenda Knowles ◽  
C. H. Ishwara-Chandra ◽  
Matt Hilton ◽  
Kavilan Moodley ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Low Frequency ◽  
Wide Field ◽  
Imaging Data ◽  
Radio Observations ◽  
Atacama Cosmology Telescope ◽  
Radio Halo ◽  
Diffuse Emissions ◽  
Compact Sources ◽  
Radio Halos

Low frequency radio observations of galaxy clusters are a useful probe of the non-thermal intracluster medium (ICM), through observations of diffuse radio emission such as radio halos and relics. Current formation theories cannot fully account for some of the observed properties of this emission. In this study, we focus on the development of interferometric techniques for extracting extended, faint diffuse emissions in the presence of bright, compact sources in wide-field and broadband continuum imaging data. We aim to apply these techniques to the study of radio halos, relics and radio mini-halos using a uniformly selected and complete sample of galaxy clusters selected via the Sunyaev-Zel’dovich (SZ) effect by the Atacama Cosmology Telescope (ACT) project, and its polarimetric extension (ACTPol). We use the upgraded Giant Metrewave Radio Telescope (uGMRT) for targeted radio observations of a sample of 40 clusters. We present an overview of our sample, confirm the detection of a radio halo in ACT−CL J0034.4+0225, and compare the narrowband and wideband analysis results for this cluster. Due to the complexity of the ACT−CL J0034.4+0225 field, we use three pipelines to process the wideband data. We conclude that the experimental spam wideband pipeline produces the best results for this particular field. However, due to the severe artefacts in the field, further analysis is required to improve the image quality.

scholarly journals Radio Sources in Clusters of Galaxies

1996 ◽  
Vol 175 ◽  
pp. 305-310
Author(s):  
F.N. Owen
Keyword(s):  
External Medium ◽  
Optical Data ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Radio Observations ◽  
X Ray

Since the Albuquerque IAU meeting, most of the advances in the understanding of radio sources in clusters has come from combining radio observations with x-ray and optical data. The x-ray images from Einstein and ROSAT have been particularly important because they have allowed us to see the external medium with which the radio sources co-exist and interact. I will cover three examples of such work in this review.

Commission 47: Cosmology (Cosmologie)

1988 ◽  
Vol 20 (1) ◽  
pp. 653-655
Author(s):  
G. Setti ◽  
K. Satco ◽  
J. Audouze ◽  
G. de Vaucouleurs ◽  
J. E. Gunn ◽  
...  
Keyword(s):  
Large Scale ◽  
Research Work ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Extragalactic Radio Sources ◽  
Vast Amount ◽  
Wide Range ◽  
Commission Report

The number of pages allocated to the commission report has been very limited and certainly not sufficient to cover in any exhaustive manner the wide range of topics relevant to cosmology and to provide also extensive bibliographies. Because of the vast amount of material to be covered, the report is based on a number of contributions from different colleagues who have been asked to highlight the main trends in the triennium (mid 1984 - mid 1987), together with a list of references sufficiently comprehensive to serve as a guideline for further reading. Unfortunately, two of the expected contributions did not reach me in time for inclusion in the report, and consequently topics such as the large scale structure and streaming motions, the clusters of galaxies and the counts of extragalactic radio sources are not included. However, it is my understanding that a large portion, if not all, of these topics will be covered in the reports of Commissions 28 and 40, and if true, this will at least avoid unnecessary overlaps. It should also be mentioned here that several proceedings of very recent IAU conferences provide excellent, updated and exhaustive reviews of the research work relevant to cosmology.

scholarly journals Clusters of Galaxies and Radio Sources

1977 ◽  
Vol 74 ◽  
pp. 305-316 ◽  
Author(s):  
Walter Jaffe
Keyword(s):  
Luminosity Function ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Cluster Environment ◽  
Different Characteristics

For some time there have been suggestions that there is a special association of radio galaxies with rich clusters of galaxies, and more recently that the radio galaxies in clusters may show different characteristics from those outside. I will discuss the evidence for three types of such differences, in luminosity function, morphology, and occurance of steep spectrum sources. In each case I will try to connect any difference I find to the cluster environment.

scholarly journals A low-frequency radio halo survey of the South Pole Telescope SZ-selected clusters with the GMRT

2020 ◽  
Vol 500 (2) ◽  
pp. 2236-2249
Author(s):  
Ramij Raja ◽  
Majidul Rahaman ◽  
Abhirup Datta ◽  
Reinout J van Weeren ◽  
Huib T Intema ◽  
...  
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Radio Sources ◽  
Synchrotron Emission ◽  
Diffuse Emission ◽  
Radio Halo ◽  
South Pole Telescope ◽  
New Radio ◽  
Upper Limits ◽  
Correlation Line

ABSTRACT The presence of non-thermal electrons and large-scale magnetic fields in the intracluster medium is known through the detection of megaparsec (Mpc) scale diffuse radio synchrotron emission. Although a significant amount of progress in finding new diffuse radio sources has happened in the last decade, most of the investigation has been constrained towards massive low-redshift clusters. In this work, we explore clusters with redshift z > 0.3 in search of diffuse radio emission, at 325 MHz with the Giant Metrewave Radio Telescope. This campaign has resulted in the discovery of two new radio haloes (SPT-CL J0013−4906 and SPT-CL J0304−4401) along with two other detections (SPT-CL J2031−4037 and SPT-CL J2248−4431), previously reported (at 325 MHz) in the literature. In addition, we detect a halo candidate in one cluster in our sample, and upper limits for haloes are placed in eight clusters where no diffuse emission is detected. In the P1.4–LX plane, the detected haloes follow the observed correlation, whereas the upper limits lie above the correlation line, indicating the possibility of future detection with sensitive observations.

scholarly journals Third-Generation Calibrations for MeerKAT Observation

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 90
Author(s):  
Viral Parekh ◽  
Robert Kincaid ◽  
Benjamin Hugo ◽  
Athanaseus Ramaila ◽  
Nadeem Oozeer
Keyword(s):  
Large Scale ◽  
Dynamic Range ◽  
Cosmic Ray ◽  
Point Sources ◽  
Formation Mechanisms ◽  
Radio Sources ◽  
Wide Field ◽  
Third Generation ◽  
Radio Observations ◽  
Wide Range

Superclusters and galaxy clusters offer a wide range of astrophysical science topics with regards to studying the evolution and distribution of galaxies, intra-cluster magnetization mediums, cosmic ray accelerations and large scale diffuse radio sources all in one observation. Recent developments in new radio telescopes and advanced calibration software have completely changed data quality that was never possible with old generation telescopes. Hence, radio observations of superclusters are a very promising avenue to gather rich information of a large-scale structure (LSS) and their formation mechanisms. These newer wide-band and wide field-of-view (FOV) observations require state-of-the-art data analysis procedures, including calibration and imaging, in order to provide deep and high dynamic range (DR) images with which to study the diffuse and faint radio emissions in supercluster environments. Sometimes, strong point sources hamper the radio observations and limit the achievement of a high DR. In this paper, we have shown the DR improvements around strong radio sources in the MeerKAT observation of the Saraswati supercluster by applying newer third-generation calibration (3GC) techniques using CubiCal and killMS software. We have also calculated the statistical parameters to quantify the improvements around strong radio sources. This analysis advocates for the use of new calibration techniques to maximize the scientific returns from new-generation telescopes.

scholarly journals Radio Surveys and Large Scale Structure

1991 ◽  
Vol 44 (6) ◽  
pp. 759 ◽  
Author(s):  
PA Shaver
Keyword(s):  
Radio Source ◽  
Large Scale ◽  
Three Dimensional ◽  
Large Scale Structure ◽  
Radio Galaxies ◽  
Scale Structure ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Normal Galaxies ◽  
Dimensional Distribution

An analysis of the Molonglo Reference Catalogue indicates that significant departures from isotropy are present in the sky distribution of strong extragalactic radio sources. This has been shown to be due to local large scale structure, specifically a concentration to the supergalactic plane, which also influences the slope of the source counts. A study of the three-dimensional distribution of local radio galaxies shows that they are more strongly concentrated to the supergalactic plane than are optically�selected galaxies, and that the supergalactic concentration is more extensive than hitherto believed. It appears that radio galaxies (and clusters of galaxies) trace the 'skeleton' of large scale structure, about which normal galaxies are more loosely distributed. Thus, while large scale structure evidently complicates the interpretation of radio source counts, it appears that radiO surveys can be of value in exploring structures on the largest scales.

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