scholarly journals The Sunyaev-Zeldovich effect from clusters of galaxies

2020 ◽  
Vol 228 ◽  
pp. 00020
Author(s):  
Etienne Pointecouteau
Keyword(s):  
Structure Formation ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
The Past ◽  
Formation And Evolution ◽  
Massive Halos

In this paper, we recall the basics of the the Sunyaev-Zeldovich effect from groups and clusters of galaxies. We review the transformational results from SZ surveys in the past decade, that have led to the detection of new clusters of galaxies from the local to the very distant Universe. The SZ effect has become a very efficient way to investigate the astrophysics of the hot intra-cluster gas, very competitive and complementary to X-ray observations. It renewed the use of massive halos as a cosmological probe or to study the physics of structure formation and evolution. We discuss the present strong synergies between the SZ and X-ray observations.

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 Space Distribution of X-Ray Clusters of Galaxies

1988 ◽  
Vol 130 ◽  
pp. 541-541
Author(s):  
A. Cavaliere ◽  
S. Colafrancesco
Keyword(s):  
Generation X ◽  
Luminosity Function ◽  
Past History ◽  
Space Distribution ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Groups Of Galaxies ◽  
The Past ◽  
History Of ◽  
Chemical Events

The Intra-Cluster Plasma constitutes an archive of the past history of all clusters and of many groups of galaxies: statistical observations of their X-ray emission will set significant constraints on the dynamical, thermal and chemical events in these cosmic structures. Data on the local X-ray luminosity function N(L, z ≃ 0) were provided by the 1st generation X-ray surveys. HEAO II provided an integral of N(L, z) out to z ≃ 0.4, the counts from a subsample of the MSS (Gioia et al. 1984, Ap.J. 283, 495): these counts result very flat, cf. Fig. 2.

scholarly journals Constraining the past X-ray luminosity of AGN in clusters of galaxies: The role of resonant scattering

2002 ◽  
Vol 393 (3) ◽  
pp. 793-807 ◽  
Author(s):  
S. Yu. Sazonov ◽  
R. A. Sunyaev ◽  
C. K. Cramphorn
Keyword(s):  
Resonant Scattering ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
The Past

scholarly journals Dark Matter in Clusters of Galaxies

1995 ◽  
Vol 164 ◽  
pp. 227-235
Author(s):  
Claude R. Canizares
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Clusters Of Galaxies ◽  
Rapid Progress ◽  
X Ray ◽  
Mass Distributions ◽  
The Past ◽  
Accurate Picture ◽  
Made In

An appropriate subtitle for this talk might be “Newton meets Einstein.” For many decades, the prime tool for studying the amount and distribution of matter in galaxy clusters was decidedly Newtonian, involving at first the measurements of the dynamics of the galaxies themselves and, for the past 15 years or so, the imputed dynamics of the hot, X-ray emitting intra-cluster gas. Einstein enters more recently with the introduction of gravitational lensing as a tool for studying cluster mass distributions. Rapid progress is being made in each of these areas, and there are now attempts to bring them together to give a consistent and more accurate picture of clusters.

scholarly journals X-Ray Observations of Clusters of Galaxies

1978 ◽  
Vol 79 ◽  
pp. 165-177 ◽  
Author(s):  
J. L. Culhane
Keyword(s):  
Optical Properties ◽  
Present Status ◽  
Luminosity Function ◽  
Cluster Structure ◽  
Current Situation ◽  
Clusters Of Galaxies ◽  
Iron Line ◽  
X Ray ◽  
The Past

X-ray astronomy has, in the past year, seen the publication of the second Ariel (2A) and fourth Uhuru (4U) catalogues of X-ray sources. A number of new X-ray cluster identifications and the confirmation of several others has resulted. in this review I will briefly summarise the situation regarding identifications and, for the 2A clusters, discuss the luminosity function and the possible relationships between a number of cluster X-ray and optical properties. Superclusters have been tentatively proposed as a class of X-ray sources and I will comment briefly on recent observations of these objects. Cluster structure has been studied by the Copernicus and SAS-3 spacecraft and by a number of rocket observations with imaging X-ray telescopes undertaken by the Harvard Centre for Astrophysics. I will review the current situation regarding structural measurements. Finally I will discuss the present status of Iron line observations at 6.7 keV in cluster spectra and the estimates of Fe abundance that result from these data.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

scholarly journals Workload for radiologists during on-call hours: dramatic increase in the past 15 years

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
R. J. M. Bruls ◽  
R. M. Kwee
Keyword(s):  
Western Europe ◽  
Kendall Test ◽  
Kendall’S Tau ◽  
Kendall's Tau ◽  
X Ray ◽  
The Past ◽  
Relative Value ◽  
Burn Out ◽  
Picture Archiving And Communication ◽  
Ct Studies

Abstract Background The objective of this study is to investigate the workload for radiologists during on-call hours and to quantify the 15-year trend in a large general hospital in Western Europe. Methods Data regarding the number of X-ray, ultrasound and computed tomography (CT) studies during on-call hours (weekdays between 6.00 p.m. and 7.00 a.m., weekends, and national holidays) between 2006 and 2020 were extracted from the picture archiving and communication system. All studies were converted into relative value units (RVUs) to estimate the on-call workload. The Mann–Kendall test was performed to assess the temporal trend. Results The total RVUs during on-call hours showed a significant increase between 2006 and 2020 (Kendall's tau-b = 0.657, p = 0.001). The overall workload in terms of RVUs during on-call hours has quadrupled. The number of X-ray studies significantly decreased (Kendall's tau-b = − 0.433, p = 0.026), whereas the number of CT studies significantly increased (Kendall's tau-b = 0.875, p < 0.001) between 2006 and 2020. CT studies which increased by more than 500% between 2006 and 2020 are CT for head trauma, brain CTA, brain CTV, chest CT (for suspected pulmonary embolism), spinal CT, neck CT, pelvic CT, and CT for suspected aortic dissection. The number of ultrasound studies did not change significantly (Kendall's tau-b = 0.202, p = 0.298). Conclusions The workload for radiologists during on-call hours increased dramatically in the past 15 years. The growing amount of CT studies is responsible for this increase. Radiologist and technician workforce should be matched to this ongoing increasing trend to avoid potential burn-out and to maintain quality and safety of radiological care.

scholarly journals A Systematic X‐Ray Search for Clusters of Galaxies behind the Milky Way. II. The Second CIZA Subsample

2007 ◽  
Vol 662 (1) ◽  
pp. 224-235 ◽  
Author(s):  
Dale D. Kocevski ◽  
Harald Ebeling ◽  
Chris R. Mullis ◽  
R. Brent Tully
Keyword(s):  
Milky Way ◽  
Clusters Of Galaxies ◽  
X Ray

scholarly journals On the relation between mini-halos and AGN feedback in clusters of galaxies

2020 ◽  
Vol 499 (2) ◽  
pp. 2934-2958
Author(s):  
A Richard-Laferrière ◽  
J Hlavacek-Larrondo ◽  
R S Nemmen ◽  
C L Rhea ◽  
G B Taylor ◽  
...  
Keyword(s):  
Large Scale ◽  
State Of The Art ◽  
Vital Role ◽  
Clusters Of Galaxies ◽  
Relativistic Jets ◽  
X Ray ◽  
Core Cluster ◽  
Central Galaxy ◽  
Central Regions ◽  
Radio Power

ABSTRACT A variety of large-scale diffuse radio structures have been identified in many clusters with the advent of new state-of-the-art facilities in radio astronomy. Among these diffuse radio structures, radio mini-halos are found in the central regions of cool core clusters. Their origin is still unknown and they are challenging to discover; less than 30 have been published to date. Based on new VLA observations, we confirmed the mini-halo in the massive strong cool core cluster PKS 0745−191 (z = 0.1028) and discovered one in the massive cool core cluster MACS J1447.4+0827 (z = 0.3755). Furthermore, using a detailed analysis of all known mini-halos, we explore the relation between mini-halos and active galactic nucleus (AGN) feedback processes from the central galaxy. We find evidence of strong, previously unknown correlations between mini-halo radio power and X-ray cavity power, and between mini-halo and the central galaxy radio power related to the relativistic jets when spectrally decomposing the AGN radio emission into a component for past outbursts and one for ongoing accretion. Overall, our study indicates that mini-halos are directly connected to the central AGN in clusters, following previous suppositions. We hypothesize that AGN feedback may be one of the dominant mechanisms giving rise to mini-halos by injecting energy into the intra-cluster medium and reaccelerating an old population of particles, while sloshing motion may drive the overall shape of mini-halos inside cold fronts. AGN feedback may therefore not only play a vital role in offsetting cooling in cool core clusters, but may also play a fundamental role in re-energizing non-thermal particles in clusters.

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