scholarly journals X-Ray Study of Clusters of Galaxies with ASCA

1999 ◽  
Vol 183 ◽  
pp. 191-199
Author(s):  
T. Ohashi
Keyword(s):  
Hydrostatic Equilibrium ◽  
Chemical Compositions ◽  
Clusters Of Galaxies ◽  
Dominant Form ◽  
X Ray ◽  
Element Abundances ◽  
Injection Mechanism ◽  
Large Systems ◽  
The Universe ◽  
Hubble Time

X-ray emission from clusters of galaxies is the most useful tool in studying mass distribution and chemical compositions in these enormously large systems. The hot intracluster medium (ICM) has been heated up to kT = 3–10 keV during the gravitational collapse, and X-ray luminosities indicate that the gas is more massive than the total galaxy mass contained in clusters by factors of 3–5. This makes ICM the dominant form of baryons in the universe. In many clusters observations indicate that ICM is in a hydrostatic equilibrium within a potential governed by the dark matter, and the cooling time is longer than the Hubble time except for the bright centers. The ICM, therefore, enables us a close look at the structure of gravitational potential. At the same time, heavy-element abundances in the ICM and their distribution are used to estimate past supernova activities and metal injection mechanism in cluster space.

scholarly journals X-ray clusters of galaxies as tracers of structure in the Universe

Nature ◽  
2001 ◽  
Vol 409 (6816) ◽  
pp. 39-45 ◽  
Author(s):  
Stefano Borgani ◽  
Luigi Guzzo
Keyword(s):  
Clusters Of Galaxies ◽  
X Ray ◽  
The Universe

Intergalactic Matter and Radiation and its Bearing on Galaxy Formation and Evolution

1974 ◽  
Vol 58 ◽  
pp. 93-108
Author(s):  
G. R. Burbidge
Keyword(s):  
Galaxy Formation ◽  
High Mass ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Hot Gas ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
The Universe ◽  
Very High ◽  
Theoretical Standpoint

An up-dated review is given of the evidence for the presence of intergalactic matter and radiation in the Universe. It is concluded that the only important constituents which may make a sizable contribution to the total mass-energy are intergalactic gas and condensed objects with a very high mass-to-light ratio. If the QSOs are not at cosmological distances, cold atomic hydrogen may still be the most important constituent and may contribute much more mass than do the galaxies. The X-ray observations still do not unambiguously show that very hot gas is present, though it is very likely on general grounds that some hot gas is present in clusters of galaxies.The question of whether or not large amounts of matter, enough to close the Universe, are present, remains unsettled. From the theoretical standpoint the answer depends almost completely on the approach taken to the problem of galaxy formation and to the cosmological model which is favoured.

scholarly journals The X-Ray Background: Origin and Implications

1980 ◽  
Vol 92 ◽  
pp. 207-225
Author(s):  
Martin J. Rees
Keyword(s):  
Large Scale ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
X Ray Background ◽  
The Universe

This paper will be concerned with three topics relevant to the X-ray background: (i) X-ray emission mechanisms in quasars; (ii) the contributions to the X-ray background from quasars, clusters of galaxies, intercluster gas, young galaxies, etc; and (iii) the use of X-ray background observations as a probe for large-scale density irregularities in the Universe.

scholarly journals Clusters of Galaxies in a Flat CHDM Universe

1998 ◽  
Vol 188 ◽  
pp. 299-299
Author(s):  
A. Habe ◽  
C. Hanyu ◽  
S. Yachi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Large Scale Structure ◽  
Numerical Results ◽  
Clusters Of Galaxies ◽  
Statistical Features ◽  
X Ray ◽  
Numerical Resolution ◽  
Radiative Processes ◽  
The Universe

Cold and hot dark matter (CHDM) model is one of viable models which can reproduce the large scale structure of the universe. HDM may affect structure of clusters of galaxies in CHDM universe. Bryan et al. (1994) gave numerical results of CHDM model that explain some statistical features of X-ray clusters of galaxies, e.g. X-ray luminosiry-temperature realtion, L ∝~ T3.5, without considering radiative processes. However their numerical resolution is insufficient to resolve the cores of X-ray clusters. So, we simulate the formation of clusters in CHDM universe more carefully.

scholarly journals NEW RESULTS FROM H.E.S.S. OBSERVATIONS OF GALAXY CLUSTERS

2009 ◽  
Vol 18 (10) ◽  
pp. 1627-1631 ◽  
Author(s):  
◽  
WILFRIED DOMAINKO ◽  
DALIBOR NEDBAL ◽  
JAMES A. HINTON ◽  
OLIVIER MARTINEAU-HUYNH
Keyword(s):  
Cosmic Rays ◽  
Galaxy Clusters ◽  
Gamma Rays ◽  
Large Scale ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Model Predictions ◽  
The Universe

Clusters of galaxies are believed to contain a significant population of cosmic rays. From the radio and probably hard X-ray bands it is known that clusters are the spatially most extended emitters of non-thermal radiation in the Universe. Due to their content of cosmic rays, galaxy clusters are also potential sources of VHE (> 100 GeV) gamma rays. Recently, the massive, nearby cluster Abell 85 has been observed with the H.E.S.S. experiment in VHE gamma rays with a very deep exposure as part of an ongoing campaign. No significant gamma-ray signal has been found at the position of the cluster. The non-detection of this object with H.E.S.S. constrains the total energy of cosmic rays in this system. For a hard spectral index of the cosmic rays of -2.1 and if the cosmic-ray energy density follows the large scale gas density profile, the limit on the fraction of energy in these non-thermal particles with respect to the total thermal energy of the intra-cluster medium is 8% for this particular cluster. This value is at the lower bounds of model predictions.

Cosmological Dark Matter

1997 ◽  
Vol 06 (04) ◽  
pp. 393-407
Author(s):  
D. N. Schramm
Keyword(s):  
Dark Matter ◽  
Light Element ◽  
Baryon Density ◽  
The Other ◽  
X Ray ◽  
Element Abundances ◽  
Baryonic Density ◽  
Cluster Data ◽  
The Universe

The basic arguments for cosmological dark matter are reviewed. It is shown that the Big Bange Nucleosynthesis constraints on the cosmological baryon density, when compared with dynamical arguments, demonstrate that the bulk of the baryons are dark and also that the bulk of the matter in the universe is nonbaryonic. The recent extragalactic deuterium observations as well as the other light element abundances were examined in detail as is the argument on the number of neutrino flavors. Arguments from recent MACHO/EROS observations of halo dark matter seem to imply that at least some of the dark baryons are in the halos of galaxies. Comparison of baryonic density arguments with recent x-ray cluster data is also made. Discussion of the interface of density and age arguments is also presented.

scholarly journals A Multi-Wavelength Analysis Of The Matter Distribution In Clusters of Galaxies

1996 ◽  
Vol 173 ◽  
pp. 157-162
Author(s):  
Haida Liang
Keyword(s):  
Gravitational Lensing ◽  
Hydrostatic Equilibrium ◽  
Clusters Of Galaxies ◽  
Matter Distribution ◽  
X Ray ◽  
Sunyaev Zel'dovich Effect ◽  
Multi Wavelength ◽  
Intermediate Redshift

We combine the X-ray data and the Sunyaev-Zel'dovich effect with the constraints from gravitational lensing for an intermediate redshift cluster to check the consistency of various mass estimates and the validity of the assumption of hydrostatic equilibrium, and to deduce the properties of the intra-cluster gas, the profile of the cluster potential and Ho.

scholarly journals Fluctuations of the Microwave Background Radiation

1978 ◽  
Vol 79 ◽  
pp. 393-404
Author(s):  
R. A. Sunyaev
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Small Scale ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
X Ray ◽  
M 10 ◽  
Microwave Background Radiation ◽  
Density Perturbations ◽  
The Universe

Investigations of small scale angular fluctuations and the spectrum of the microwave background radiation is one of the main methods of studying the large scale structure of the Universe. Figure 1 shows the principal stages of the evolution of the Universe. Today we can directly observe galaxies, clusters of galaxies and quasars in the redshift range z ≤ 3.5 by optical, radio and X-ray astronomy. These observations show that significant density perturbations δρ/ρ > 1 are present on mass scales M < 1016 M⊙. the Universe is essentially uniform δρ/ρ < 1 on large scales M ≫ 1016 M⊙.

Beyond the Schwarzschild Metric

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Gravitational Waves ◽  
Test Particle ◽  
Direct Detection ◽  
Relativistic Effects ◽  
Big Bang ◽  
Clusters Of Galaxies ◽  
General Relativistic ◽  
The Universe

General relativity explains much more than the spacetime around static spherical masses.We briefly assess general relativity in the larger context of physical theories, then explore various general relativistic effects that have no Newtonian analog. First, source massmotion gives rise to gravitomagnetic effects on test particles.These effects also depend on the velocity of the test particle, which has substantial implications for orbits around black holes to be further explored in Chapter 20. Second, any changes in the sourcemass ripple outward as gravitational waves, and we tell the century‐long story from the prediction of gravitational waves to their first direct detection in 2015. Third, the deflection of light by galaxies and clusters of galaxies allows us to map the amount and distribution of mass in the universe in astonishing detail. Finally, general relativity enables modeling the universe as a whole, and we explore the resulting Big Bang cosmology.

scholarly journals New Insights into the Crystal Chemistry of Elpidite, Na2Zr[Si6O15]·3H2O and (Na1+YCax□1−X−Y)Σ=2Zr[Si6O15]·(3−X)H2O, and Ab Initio Modeling of IR Spectra

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2160
Author(s):  
Alexander Bogdanov ◽  
Ekaterina Kaneva ◽  
Roman Shendrik
Keyword(s):  
Ir Spectra ◽  
Structural Models ◽  
Chemical Characterization ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Special Group ◽  
X Ray ◽  
Influence Of Water ◽  
Radioactive Species

Elpidite belongs to a special group of microporous zirconosilicates, which are of great interest due to their capability to uptake various molecules and ions, e.g., some radioactive species, in their structural voids. The results of a combined electron probe microanalysis and single-crystal X-ray diffraction study of the crystals of elpidite from Burpala (Russia) and Khan-Bogdo (Mongolia) deposits are reported. Some differences in the chemical compositions are observed and substitution at several structural positions within the structure of the compounds are noted. Based on the obtained results, a detailed crystal–chemical characterization of the elpidites under study was carried out. Three different structure models of elpidite were simulated: Na2ZrSi6O15·3H2O (related to the structure of Russian elpidite), partly Ca-replaced Na1.5Ca0.25ZrSi6O15·2.75H2O (close to elpidite from Mongolia), and a hypothetical CaZrSi6O15·2H2O. The vibration spectra of the models were obtained and compared with the experimental one, taken from the literature. The strong influence of water molecule vibrations on the shape of IR spectra of studied structural models of elpidite is discussed in the paper.

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