EUV AND SOFT X–RAYS FROM CLUSTERS OF GALAXIES – THE 'CLUSTER SOFT–EXCESS' PHENOMENON

Data from the UHURU satellite have provided a list of more than forty high latitude sources (|b| > 20°). X-rays have been detected from among the nearest normal galaxies, giant radio galaxies, Seyferts, QSOs and clusters of galaxies. The cluster sources appear to be extended by several hundred kiloparsecs as well as being very luminous. These cluster sources have systematic differences in their X-ray spectra from individual galaxies.About twenty sources are not reliably identified so far. A few of these are located near undistinguished 3C or MSH radio sources. The rest are either located near distant clusters or undistinguished bright galaxies, or are too far south, so that we have not sufficient optical data to allow a thorough search for possible association with clusters or unusual individual galaxies.The luminosity function for weak, high latitude X-ray sources is determined, and the contribution of sources just below the UHURU threshold of detectability to observed fluctuations in the diffuse X-ray background is evaluated. The total contribution of all observed types of extragalactic sources to the X-ray background is estimated.

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X-RAYS FROM CLUSTERS OF GALAXIES

Texas in Tuscany ◽

10.1142/9789812704009_0018 ◽

2003 ◽

Cited By ~ 1

Author(s):

A.C. FABIAN ◽

S.W. ALLEN

Keyword(s):

Clusters Of Galaxies ◽

X Rays

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CLUSTERS OF GALAXIES IN X-RAYS

Exploring the Universe ◽

10.1142/9789812792174_0010 ◽

2000 ◽

Author(s):

A. CAVALIERE

Keyword(s):

Clusters Of Galaxies ◽

X Rays

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Development of New Analysis Method for Mapping Observations of Clusters of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s007418090011530x ◽

1998 ◽

Vol 188 ◽

pp. 312-313

Author(s):

K. Kikuchi ◽

T. Ohashi ◽

H. Ezawa ◽

M. Hirayama ◽

H. Honda ◽

...

Keyword(s):

Surface Brightness ◽

Stray Light ◽

Physical Parameters ◽

Clusters Of Galaxies ◽

X Rays ◽

X Ray ◽

Hot Gas ◽

Cluster Data ◽

Metal Abundance ◽

Analysis System

Mapping observations of nearby large-extended clusters of galaxies (Coma, Perseus, Virgo, etc.) are being performed with ASCA. Such clusters allow us to map physical parameters of hot gas in the clusters, such as temperature, metal abundance, and X-ray surface brightness. To determine such parameters at each part of a cluster, one should take careful care of X-ray contamination from outside of a pointed field, which is mainly due to “stray-light” X-rays (Honda et al. 1997). For this reason, the only way to obtain the distribution of hot gas parameter is to process the whole cluster data in a self-consistent way. For this purpose, we are developing the new analysis system called TERRA.

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X-Rays from Galaxies and Clusters of Galaxies: Observations and Phenomenology

Symposium - International Astronomical Union ◽

10.1017/s0074180900150168 ◽

1987 ◽

Vol 117 ◽

pp. 165-181 ◽

Cited By ~ 2

Author(s):

C. R. Canizares

Keyword(s):

Direct Evidence ◽

Temperature Profiles ◽

Clusters Of Galaxies ◽

X Rays ◽

Early Type ◽

X Ray ◽

Cluster Galaxies ◽

Cooling Flows ◽

Hot Gas ◽

Relevant Work

X-Ray observations of galaxies and clusters can, in principle, trace the binding mass in these systems. I review some of the relevant work. The mass of hot gas in rich clusters is comparable to or exceeds the mass in visible stars. This proportion of gas to stellar material could be universal, although there is no direct evidence that it must be. Studies of the distribution of the gas indicate the presence of dark matter in the envelopes of some dominant cluster galaxies, most notably M87. The M/LB values increase with radius to values of ∼ 400–600 M⊙/L⊙. Uncertainties in the temperature distribution of the gas have hampered these analyses and have made it difficult to draw definitive conclusions about the binding mass in clusters. Recent work on Coma suggests that M/L is falling with radius and the total M/L for the cluster may be as low as ∼ 120. Studies of early type galaxies show that many contain hot gas with temperatures ∼107 K. There is evidence for the existence of cooling flows, and gravity rather than supernovae may be the dominant source of energy that heats the gas. The deduced binding masses for several bright galaxies are uncertain because of the unknown temperature profiles. Values of M/LB ≃ 20–30 within ∼ 30–40 kpc are indicated if one assumes isothermality, but values as low as 5 and as high as 100 are allowed. With better models one may be able to reduce these uncertainties.

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GRAVITATIONAL COLLAPSE AND NON-SELF-SIMILARITY IN THE L–T RELATION

International Journal of Modern Physics D ◽

10.1142/s0218271805006122 ◽

2005 ◽

Vol 14 (05) ◽

pp. 849-859

Author(s):

ANTONINO DEL POPOLO ◽

N. ERCAN ◽

N. HIOTELIS

Keyword(s):

Angular Momentum ◽

Gravitational Collapse ◽

External Pressure ◽

Fundamental Result ◽

Clusters Of Galaxies ◽

X Rays ◽

Self Similarity ◽

Temperature Relation ◽

Pressure Term ◽

Self Similar

We derive the luminosity–temperature relation for clusters of galaxies by means of a modification of the self-similar model to take account of angular momentum acquisition by protostructures and of an external pressure term in the virial theorem. We show that the above effect leads, in X-rays, to a luminosity–temperature relation that scales as L ∝ T5, at scale of groups, flattening to L ∝ T3 for rich clusters and converging to L ∝ T2 at higher temperatures. The fundamental result of the model is that gravitational collapse, which takes account of angular momentum acquisition, can explain the non-self-similarity in the L–T relation, in disagreement with the largely accepted assumption that heating/cooling processes and similar are fundamental in the originating the non-self-similar behavior (shaping) of the L–T relation.

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Hot Gas in Clusters of Galaxies

Highlights of Astronomy ◽

10.1017/s1539299600004135 ◽

1980 ◽

Vol 5 ◽

pp. 387-396

Author(s):

J. L. Culhane

Keyword(s):

Surface Brightness ◽

Luminosity Function ◽

Clusters Of Galaxies ◽

X Rays ◽

Will Emit ◽

X Ray ◽

Hot Gas ◽

Sky Survey ◽

To Come ◽

Einstein Observatory

The discovery of extended X-ray sources associated with clusters of galaxies which resulted from the Uhuru X-ray sky survey was one of the most important observations to come from that programme. Following Uhuru, the Ariel V and HEAO-1 sky surveys have found many more cluster X-ray sources and the recently launched Einstein observatory has begun to increase further the number of identifications. However there is in any case evidence from the X-ray cluster luminosity function that all rich clusters of galaxies will emit X-rays at some level.Preliminary results from the Einstein observatory (Murray, 1979) suggest that the extended X-ray emission from centrally condensed (cD) clusters is itself centrally condensed and spherically symmetrical in appearance. However irregular clusters have non-uniform X-ray surface brightness distributions. In addition there are some galaxies in clusters of irregular morphology that have associated X-ray halos.

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