scholarly journals Implications of Results from The Einstein Observatory for The X-Ray Background

1980 ◽  
Vol 5 ◽  
pp. 763-770
Author(s):  
Paul Gorenstein ◽  
Daniel A. Schwartz
Keyword(s):  
Galaxy Formation ◽  
Large Mass ◽  
X Ray ◽  
Hot Plasma ◽  
Diffuse Background ◽  
Points Of View ◽  
X Ray Background ◽  
Most Probable Explanation ◽  
The Universe ◽  
Einstein Observatory

The origin of the diffuse background has been an important question in X-ray astronomy starting from the earliest measurements (Giacconi, et al. 1962). When it was recognized that the X-ray background above 2 keV was isotropic and hence extragalactic (c.f. Schwartz 1970, 1979), it became evident that understanding its origin would have cosmological implications (c.f. Hoyle 1963, Rees 1973). Two general explanations representing opposite points of view have received the most attention. One is that the background is composed of faint unresolved objects which are of the same classes as, but perhaps in earlier phases than, the objects which can be detected directly and identified. If this explanation is correct, then the luminosities and/or proper densities of the objects must be larger at earlier times in the universe, and the magnitude and graininess of the background can be used to place important constraints upon the evolution of the objects. The other is that the background is truly diffuse. The most probable explanation of this type is a hot plasma that pervades the intergalactic medium. If it accounted for only 10% of the background, the mass that could be attributed to such a plasma would represent more matter in the universe than has been detected so far by all other means. Such a large mass would be important dynamically, and in determining the deceleration parameter, although it would not “close” the universe. Furthermore, the density of such a plasma would place constraints upon determining the epoch of galaxy formation.

scholarly journals 1/4 Ke V Diffuse Background and the Local Interstellar Medium

1989 ◽  
Vol 120 ◽  
pp. 536-536
Author(s):  
S.L. Snowden
Keyword(s):  
Interstellar Medium ◽  
Filling Factor ◽  
Thermal Emission ◽  
Mean Free Path ◽  
Physical Parameters ◽  
X Rays ◽  
Local Interstellar Medium ◽  
X Ray ◽  
Diffuse Background ◽  
X Ray Background

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

scholarly journals 9.18. Galactic winds in active galaxies

1998 ◽  
Vol 184 ◽  
pp. 417-418 ◽  
Author(s):  
S. Veilleux ◽  
J. Bland-Hawthorn ◽  
G. Cecil ◽  
P. Shopbell
Keyword(s):  
Absorption Line ◽  
Galaxy Formation ◽  
Large Scale ◽  
Large Scale Structure ◽  
Active Galaxies ◽  
Large Scale Circulation ◽  
X Ray ◽  
Hubble Sequence ◽  
Galactic Winds ◽  
X Ray Background

The effects of large-scale galactic winds in active galaxies may be far-reaching. It has been suggested that the Hubble sequence can be understood in terms of a galaxy's greater ability to sustain winds with increasing bulge-to-disk ratio. The large-scale circulation of gas associated with these galactic winds might help explain the mass-metallicity relation between galaxies and the metallicity-radius relation within galaxies. Galactic winds probably contribute non-negligibly to the cosmic X-ray background and may be involved in the quasar absorption-line phenomenon. The cosmological implications of the wind phenomenon have been widely explored in the context of proto-galaxies and quasars. The extremely energetic galactic winds that were likely associated with galaxy formation almost certainly played a key role in heating and ionizing the intergalactic medium at high redshifts and may have created the seeds for the large-scale structure we see today.

scholarly journals Soft X-rays from the Galaxy

1970 ◽  
Vol 37 ◽  
pp. 406-407
Author(s):  
M. J. Rees
Keyword(s):  
Galactic Plane ◽  
Galactic Latitude ◽  
X Rays ◽  
Indirect Methods ◽  
X Ray ◽  
Background Data ◽  
Diffuse Background ◽  
The Galaxy ◽  
X Ray Background ◽  
Significant Flux

Below 1 keV, analyses of X-ray background data are complicated by galactic absorption effects, which cause the received intensity to vary with galactic latitude. Bowyer et al. (1968) observed that the diffuse background did not fall off as rapidly as was expected towards the galactic plane. One plausible interpretation of their data would be to suppose that a significant flux of soft X-rays emanates from the disc itself. I wish to discuss what could be inferred about the latter component from improved observations of its latitude-dependence, and by indirect methods.

scholarly journals The Soft X-ray Background Spectrum from DXS

1997 ◽  
Vol 166 ◽  
pp. 83-90 ◽  
Author(s):  
W.T. Sanders ◽  
R.J. Edgar ◽  
D.A. Liedahl ◽  
J.P. Morgenthaler
Keyword(s):  
Galactic Plane ◽  
Emission Lines ◽  
Background Spectrum ◽  
Local Bubble ◽  
X Ray ◽  
Hot Plasma ◽  
Solar Abundances ◽  
Ionic Emission ◽  
X Ray Background ◽  
Ionization Balance

AbstractThe Diffuse X-ray Spectrometer (DXS) obtained spectra of the low energy X-ray (44 – 83 Å) diffuse background near the galactic plane from galactic longitudes 150° ≲ l ≲ 300° with ≲ 3 Å spectral resolution and ~ 15° angular resolution. Thus, DXS measured X-ray spectra that arise almost entirely from within the Local Bubble. The DXS spectra show emission lines and emission-line blends, indicating that the source of the X-ray emission is thermal – hot plasma in the Local Bubble. The measured spectra are not consistent with those predicted by standard coronal models, either with solar abundances or depleted abundances, over the temperature range 105 – 107 K. The measured spectra are also inconsistent with the predictions of various non-equilibrium models. A nearly acceptable fit to DXS spectra can be achieved using a hybrid model that combines the Raymond & Smith ionization balance calculation with recently calculated (by DAL) ionic emission lines.

scholarly journals Quasar Contribution to the X-Ray Background

1981 ◽  
Vol 94 ◽  
pp. 273-274
Author(s):  
Ajit Kembhavi ◽  
A. C. Fabian
Keyword(s):  
X Ray ◽  
Statistical Correlations ◽  
Wide Range ◽  
X Ray Background ◽  
Einstein Observatory ◽  
Insight Into

Recent observations by the Einstein Observatory have shown that a majority of known quasars are powerful X-ray emitters. The 107 objects observed as of Feb. 1980 (Zamorani et al. 1980) have X-ray, optical and radio luminosities scattered over a wide range. Until a large enough X-ray selected sample of quasars becomes available, it is necessary to study statistical correlations in the available sample, so that some insight into X-ray production may be obtained, and the contribution of quasars to the X-ray background estimated.

scholarly journals Small-Scale Fluctuations and Anisotropies in the 1–3 keV X-Ray Background

1990 ◽  
Vol 139 ◽  
pp. 408-409
Author(s):  
X. Barcons ◽  
A. C. Fabian
Keyword(s):  
Spatial Distribution ◽  
Probability Distribution ◽  
Proportional Counter ◽  
Flux Distribution ◽  
Small Scale ◽  
X Ray ◽  
Deep Survey ◽  
X Ray Background ◽  
Einstein Observatory ◽  
Source Number

The spatial distribution of the 1–3 keV X-ray background (XRB) in five Einstein Observatory Imaging Proportional Counter fields has been analyzed. The autocorrelation function does not exceed 9% on scales ~5′. The observed count probability distribution is then used to check the source number-flux distribution at faint levels. Agreement with the Einstein Observatory deep survey is obtained. A cutoff in the number-flux distribution for a Euclidean population of sources at a flux approximately one-half of the deep survey limit, previously suggested by Hamilton and Helfand (1987), is also inferred.

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 in Isotropic World Models

1969 ◽  
Vol 22 (4) ◽  
pp. 521 ◽  
Author(s):  
AD Payne
Keyword(s):  
Characteristic Time ◽  
Cosmic Ray ◽  
Black Body ◽  
Black Body Radiation ◽  
Fast Electrons ◽  
X Ray ◽  
Intergalactic Space ◽  
Source Spectra ◽  
X Ray Background ◽  
The Universe

This paper is an attempt to describe the diffuse X-ray background in terms of Compton radiation from cosmic ray electrons in intergalactic space. Similarities between the X-ray and radio source spectra suggest that fast electrons escape more or less freely from radio galaxies. It is assumed that the time scale of electron injection is small compared with the characteristic time of evolution of the universe. The electrons are considered to lose energy through Compton scattering (due to the presence of the universal black-body radiation at 3�K) and by expansion of the coordinate system.

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