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.

scholarly journals Observational Properties of Diffuse Halos in Clusters

2002 ◽  
Vol 199 ◽  
pp. 133-140 ◽  
Author(s):  
Luigina Feretti
Keyword(s):  
Thermal Plasma ◽  
Statistical Properties ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Diffuse Sources

The number of known diffuse radio sources in clusters of galaxies has grown in recent years, making it possible to derive statistical properties of these sources and of the hosting clusters. We show that diffuse sources are associated with X-ray luminous clusters which have undergone recent merger processes. The radio and X-ray structures are often similar, and correlations are found between radio and X-ray parameters. This is indication of a link between the diffuse relativistic and thermal plasma in clusters of galaxies.

scholarly journals Color Maps of A 1795 and A 2597 - Cooling Flow Cluster Central Galaxies with Active Nuclei

1989 ◽  
Vol 134 ◽  
pp. 460-461
Author(s):  
W. Romanishin
Keyword(s):  
Star Formation ◽  
Clusters Of Galaxies ◽  
Nuclear Activity ◽  
X Ray ◽  
Cluster Galaxies ◽  
Cooling Flows ◽  
Cooling Flow ◽  
Show Evidence ◽  
The Subject ◽  
Optical Manifestation

The subject of cooling flows in clusters of galaxies remains a controversial one, primarily because many clusters which have large x-ray derived mass inflow rates do not show any optical manifestation of the inflow or of the final fate of the gas. However, a handful of cooling flow clusters do show extended blue continuum regions indicative of current star formation which may be caused by the cooling flows (Romanishin 1987, Romanishin and Hintzen 1988), while another group show spectral evidence of star formation (O'Connell and McNamara 1988). Most of the cluster galaxies which show evidence of star formation also show nuclear activity, in the form of radio emission.

scholarly journals The Intergalactic Medium

1982 ◽  
Vol 97 ◽  
pp. 453-459
Author(s):  
A. C. Fabian ◽  
A. K. Kembhavi
Keyword(s):  
Radio Emission ◽  
Intergalactic Medium ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Intergalactic Gas ◽  
X Ray ◽  
Extended Radio ◽  
X Ray Background ◽  
Ngc 1275 ◽  
Intracluster Gas

The density of intergalactic gas may be an important parameter in the formation of extended radio sources. It may range from ∼ 0.1 particle cm−3 in the centres of some rich clusters of galaxies down to 10−8cm−3 or less in intercluster space. The possible influence of the intracluster gas surrounding NGC 1275 on its radio emission is discussed, and the possibility that a significant fraction of the X-ray background is due to a hot intergalactic medium is explored in some detail.

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.

Steep-Spectrum Radio Sources in Clusters of Galaxies—The Southern Sample

1984 ◽  
Vol 5 (4) ◽  
pp. 516-529 ◽  
Author(s):  
O. B. Slee ◽  
J. E. Reynolds
Keyword(s):  
Radio Galaxies ◽  
High Energy ◽  
Radio Spectrum ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Detailed Review ◽  
X Ray ◽  
High Energy Electrons ◽  
Spectrum Radio ◽  
Inverse Compton

It is well established (e.g. Slee et al. 1983) that radio galaxies near the centres of rich clusters of galaxies tend to have steeper radio spectra than field radio galaxies. The fact that the sources with the steepest spectra occur in clusters that are highly luminous X-ray emitters has generally been interpreted in terms of the confining influence of a hot (~108 K), relatively dense (10-2 to 10-3 electrons cm-3) intra-cluster gas; the confined relativistic plasma then preferentially loses its high-energy electrons through synchrotron and inverse Compton losses, resulting in a steepening of the radio spectrum. A more detailed review of the evidence for this process is given by Robertson (1983).

scholarly journals Radio Halos and Relics in Clusters of Galaxies and Detection Statistics

2002 ◽  
Vol 199 ◽  
pp. 149-150 ◽  
Author(s):  
Gabriele Giovannini ◽  
Luigina Feretti ◽  
Federica Govoni
Keyword(s):  
Clusters Of Galaxies ◽  
Diffuse Emission ◽  
X Ray ◽  
Abell Clusters ◽  
Radio Halos

New sensitive VLA observations confirm the existence of halo and relic sources in 6 Abell clusters where a diffuse emission was found in the NVSS.We find evidence that the frequency of clusters with halos and relics is larger in clusters with high X-ray luminosity. The evidence that the occurrence of a halo source is larger at high redshifts is marginal.

Radio Galaxies and Quasars in Clusters of Galaxies

1983 ◽  
Vol 5 (2) ◽  
pp. 144-151 ◽  
Author(s):  
J. Gordon Robertson
Keyword(s):  
Radio Galaxies ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Intracluster Medium ◽  
X Ray ◽  
Broad Field

The study of radio galaxies situated within clusters of galaxies has become a broad field, with hundreds of papers published in the last few years. This review will therefore be restricted mainly to consideration of the interactions between the extended components of radio sources in clusters and the diffuse gas (intracluster medium, ICM) which occurs in clusters. In particular, attention will be focused on what we can learn about the ICM from this interaction, in conjunction with other data such as X-ray observations. In the case of quasars in clusters of galaxies the emphasis is rather different, so discussion of this topic is deferred to section 6.

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 X-Ray Substructures of BCS, NORAS, REFLEX, Radio Halos/Relics and Cooling Flow Clusters of Galaxies

2002 ◽  
Vol 12 ◽  
pp. 519-521 ◽  
Author(s):  
Peter Schuecker ◽  
Hans Böhringer ◽  
Luigina Feretti
Keyword(s):  
Systematic Study ◽  
Surface Brightness ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Radio Halo ◽  
Cooling Flow ◽  
Cluster Morphology ◽  
Density Relation ◽  
Radio Halos

AbstractThe results of a systematic study of substructures in X-ray surface brightness distributions of BCS, NORAS, REFLEX, radio halo, relic, and cooling flow clusters of galaxies based on RASS data are presented. At least 40 percent of the clusters show substructure. Indications for a cluster morphology-density relation are found. The fraction of clusters with substructure seems to be higher for halo and relic clusters and lower for clusters with cooling flow signature.

scholarly journals A comparison of radio and X-ray morphologies of four clusters of galaxies containing radio halos

2001 ◽  
Vol 369 (2) ◽  
pp. 441-449 ◽  
Author(s):  
F. Govoni ◽  
T. A. Enßlin ◽  
L. Feretti ◽  
G. Giovannini
Keyword(s):  
Clusters Of Galaxies ◽  
X Ray ◽  
Radio Halos
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