scholarly journals Radio Sources in Clusters of Galaxies

1968 ◽  
Vol 21 (4) ◽  
pp. 511 ◽  
Author(s):  
BY Mills ◽  
RR Shobbrook ◽  
D Stewart-Richardson
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Cluster Galaxy ◽  
Stellar Objects ◽  
Cluster Emission ◽  
Cluster Galaxies ◽  
Individual Cluster

Fifty-eight clusters from Abell's catalogue have been examined for radio emission using the Arecibo l000 ft reflector and the Molonglo 1 mile Cross. The positions, sizes, and flux densities at 408 MHz of 30 radio sources close to these clusters have been measured. Nineteen of these offer reasonable identifications with galaxies or blue stellar objects. Thirteen appear to be identifiable with individual cluster galaxies. No evidence for integrated cluster emission has been obtained. It has been concluded that either the centroid of radio sources may sometimes be well displaced from the parent galaxies or, in a significant number of cases, the only detectable radio source in a cluster is associated with a faint cluster galaxy, not a giant.

Powerful Radio Sources in Clusters of Galaxies

1991 ◽  
Vol 9 (1) ◽  
pp. 100-102
Author(s):  
A. M. Unewisse ◽  
R. W. Hunstead
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Flux Density ◽  
Radio Sources ◽  
High Flux ◽  
Clusters Of Galaxies ◽  
Powerful Radio ◽  
Complete Sample ◽  
Cluster Galaxies ◽  
Cluster Centre

AbstractUsing a complete sample, we have looked for correlations in position between radio sources with S408 ≥ 1 Jy in the Molonglo Reference Catalogue (MRC) and rich clusters of galaxies in the Abell, Corwin and Olowin catalogue (ACO). Within a projected radius of 100 kpc of the cluster centre, we find an overdensity of radio sources similar to that seen by Robertson and Roach (1990). They attributed this feature to centrally located dominant cluster galaxies. We confirm this hypothesis by looking at the morphology of the clusters within this peak and by optically identifying galaxies associated with the radio emission. Due to the relatively high flux density limit imposed, the cluster radio sources in this sample are among the most powerful in the southern sky. The probability of a cluster containing a radio source of this power is found not to depend on cluster richness.

scholarly journals Clusters with extended radio emission at high frequencies

1978 ◽  
Vol 79 ◽  
pp. 157-159
Author(s):  
R. Wielebinski
Keyword(s):  
Radio Emission ◽  
Direct Measurement ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Coma Cluster ◽  
Extended Source ◽  
High Frequencies ◽  
Extended Radio ◽  
Extended Component ◽  
Perseus Cluster

The existence of ‘haloes’ in clusters of galaxies was deduced by Ryle and Windram (1968) for the Perseus cluster and by Willson (1970) for the Coma cluster at 408 MHz by comparing total flux measured by a single dish with the sum of fluxes of radio sources found in the field. A direct measurement of the extended source Coma C was made by Jaffe et al. (1976) at 610 MHz. the failure to detect the halo of Coma at higher frequencies is attributed by all authors to a steep spectrum of this extended component.

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 The Compact Nonthermal Radio Source at the Galactic Center: an Update

1989 ◽  
Vol 136 ◽  
pp. 527-534
Author(s):  
K. Y. Lo
Keyword(s):  
Radio Source ◽  
Galactic Center ◽  
Central Star ◽  
Radio Sources ◽  
Stellar Objects ◽  
Nonthermal Radio ◽  
Compact Radio Source ◽  
The Galaxy ◽  
Observational Status ◽  
Sgr A

We review the current observational status of Sgr A∗, the compact nonthermal radio source at the galactic center. Sgr A∗ is a unique radio source at a unique location of the Galaxy. It is unlike any compact radio source associated with known stellar objects, but it is similar to extragalactic nuclear compact radio sources. The positional offset between Sgr A∗ and IRS16 places little constraint on the nature of the underlying energy source, since IRS16 need not be the core of the central star cluster. Sgr A∗ is still the best candidate for marking the location of a massive collapsed object.

scholarly journals Radio Emission from Clusters of Galaxies

1967 ◽  
Vol 20 (6) ◽  
pp. 715 ◽  
Author(s):  
HM Tovmassian ◽  
IG Moiseev
Keyword(s):  
Radio Emission ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Mathematical Expectation ◽  
Astronomical Observatory ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Astronomy Observatory ◽  
Group 5 ◽  
East West

From Abell's (1958) list of clusters of galaxies, 137 clusters of distance group 5 were observed at 1410 MHz with the 210 ft radio telescope of the Australian National Radio Astronomy Observatory at Parkes. The detected radio sources were further confirmed hy observations at 2650 MHz with the same telescope and at 408 MHz with the east-west arm of the Mills Cross at the Molonglo Radio Astronomical Observatory. A total of 25 radio sources was detected within 5' arc of the centres of corresponding clusters of galaxies, while the mathematical expectation of the number of random coincidences with clusters is about two or three

scholarly journals A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

2019 ◽  
Vol 486 (1) ◽  
pp. L80-L84 ◽  
Author(s):  
Ruta Kale ◽  
Krishna M Shende ◽  
Viral Parekh
Keyword(s):  
Radio Source ◽  
Surface Brightness ◽  
Galaxy Cluster ◽  
Cosmic Ray ◽  
Radio Sources ◽  
Cluster Galaxy ◽  
X Ray ◽  
Radio Halo ◽  
The Galaxy ◽  
Radio Power

ABSTRACT Diffuse radio sources associated with the intra-cluster medium are direct probes of the cosmic ray electrons and magnetic fields. We report the discovery of a diffuse radio source in the galaxy cluster RXCJ0232.2–4420 (SPT-CL J0232–4421, z = 0.2836) using 606 MHz observations with the Giant Metrewave Radio Telescope. The diffuse radio source surrounds the Brightest Cluster Galaxy in the cluster-like typical radio mini-haloes. However the total extent of it is 550 × 800 kpc2, which is larger than mini-haloes and similar to that of radio haloes. The BCG itself is also a radio source with a marginally resolved core at 7 arcsec (30 kpc) resolution. We measure the 606 MHz flux density of the RH to be 52 ± 5 mJy. Assuming a spectral index of 1.3, the 1.4 GHz radio power is 4.5 × 1024 W Hz−1. The dynamical state of the cluster has been inferred to be 'relaxed’ and also as 'complex’, depending on the classification methods based on the morphology of the X-ray surface brightness. This system thus seems to be in the transition phase from a mini-halo to a radio halo.

scholarly journals Properties of Radio Sources in Clusters of Galaxies

1977 ◽  
Vol 4 (1) ◽  
pp. 321-328 ◽  
Author(s):  
Daniel E. Harris
Keyword(s):  
Radio Source ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Coma Cluster ◽  
Cluster A

“The properties of radio sources in clusters” presupposes that we know something about radio sources out of clusters, or that we even know whether a radio source is “in” or “out” of a cluster. Thus we are faced with the problem of defining what we mean by a cluster. Most of us use Abell’s catalogue of RICH clusters and assume that we are really “in” a cluster. However, most radio sources are identified with faint, distant objects and it is often difficult to know whether the remark “galaxy in a group” or “galaxy in a cluster” indicates a cluster such as the Coma Cluster, a cluster similar to an “open” Zwicky cluster, or a group of galaxies which may be gravitationally bound.This uncertainty must not be forgotten, and in the following discussion, we will try to limit the effects of this by concentrating on catalogued clusters; ignoring most distant radio galaxies, many of which may be in rich clusters; and also by neglecting quasars, some or all of which may be in clusters.

scholarly journals Observations of Radio Emission from Normal Galaxies

1963 ◽  
Vol 16 (3) ◽  
pp. 360 ◽  
Author(s):  
DS Mathewson ◽  
JM Rome
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Spiral Galaxies ◽  
Radio Sources ◽  
Early Type ◽  
General Belief ◽  
Normal Galaxies ◽  
Discrete Radio Sources

The results of observations of 37 normal galaxies using the 21O-ft steerable reflector of the A.N.R.A.O. at 1410 and 408 Mcls are presented. All southern galaxies brighter than tenth magnitude were studied. Twenty galaxies were detected, fourteen of which were new identifIcationis. Sc galaxies were found to have a mean radio index at 1410 Mcls of +3�3 with an r.m.s. deviation of 0�6. The ratio of optical to radio emission was signifIcantly higher for irregular and early type galaxies than for Sb and Sc galaxies_ Contrary to general belief, no constant relationship was found between the optical and radio sizes of spiral galaxies. Two discrete radio sources were detected in the Pegasus I cluster, one of which may be identified with the El galaxy, NGC 7626. The radio source found in Pegasus II coincided in position with the E3 galaxy, NGC 7501, in the cluster.

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.

scholarly journals The High-Redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey

2015 ◽  
Vol 11 (S319) ◽  
pp. 62-62
Author(s):  
Rachel Paterno-Mahler ◽  
Elizabeth L. Blanton ◽  
Joshua Wing ◽  
M.L.N. Ashby ◽  
Mark Brodwin ◽  
...  
Keyword(s):  
Radio Source ◽  
Galaxy Clusters ◽  
Large Range ◽  
High Redshift ◽  
Cosmic Time ◽  
Optical Data ◽  
Radio Sources ◽  
Cluster Galaxies ◽  
Redshift Galaxy ◽  
Red Sequence

AbstractThe number of confirmed, high-redshift galaxy clusters is very low compared to the number of well-studied clusters nearby. Bent, double-lobed radio sources are frequently found in galaxy clusters, and thus can be used as tracers for efficiently locating high-redshift clusters. Using our Spitzer Snapshot Survey, we have identified approximately 300 potential new clusters with redshifts 0.7 < z < 3. These objects make up the high-redshift portion of the Cluster Occupied by Bent Radio AGN (COBRA) survey. We have created color-magnitude diagrams using infrared and optical data. Using the colors of the radio source host and the red sequence we can estimate redshifts for our clusters, as well as examine the evolution of the cluster galaxies over a large range of cosmic time.

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