scholarly journals Extragalactic X-Ray Sources and Their Contribution to the Diffuse Background: Invited Paper

1973 ◽  
Vol 55 ◽  
pp. 208-211 ◽  
Author(s):  
G. Setti ◽  
L. Woltjer
Keyword(s):  
Radio Galaxies ◽  
Energy Interval ◽  
Background Intensity ◽  
X Ray ◽  
Diffuse Background ◽  
Decisive Test ◽  
Quasistellar Objects ◽  
X Ray Background

We present estimates of the integrated contribution of extragalactic sources to the diffuse X-ray background in the 2–10 keV energy interval. It appears that classes of objects already detected as X-ray sources easily account for at least 10% of the background. Quasistellar objects, and possibly Seyfert and radio galaxies might contribute a larger fraction of the background intensity.We also suggest that several of the unidentified X-ray sources in the UHURU catalogue at high galactic latitudes may be bright QSO's as yet unknown. The detection of a larger number of QSO's in the X-ray band may allow a decisive test for the cosmological interpretation of the redshifts of QSO's.

scholarly journals HEAO-1 Diffuse Soft X-Ray Sky Maps

1984 ◽  
Vol 81 ◽  
pp. 219-221
Author(s):  
John A. Nousek ◽  
Gordon P. Garmire ◽  
George Weaver
Keyword(s):  
Galactic Center ◽  
Energy Interval ◽  
Background Intensity ◽  
X Ray ◽  
The North ◽  
Center Region ◽  
Local Emission ◽  
North Polar ◽  
X Ray Background

Maps of the diffuse soft X-ray background intensity are presented, spanning four energy intervals. The lowest energy interval (0.18-0.56 keV) is dominated by local emission, while the next two intervals (0.56-1.0 keV and 1.0-1.4 keV) reveal more distant and more sharply defined structures. Enlarged maps of several of these structures are presented, including the North Polar Spur, the Galactic Center region and the Eridanus Loop.

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 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 X-ray Constraints on AGN Clustering

1989 ◽  
Vol 134 ◽  
pp. 492-493
Author(s):  
G. De Zotti ◽  
M. Persic ◽  
A. Franceschini ◽  
L. Danese ◽  
G.G.C. Palumbo ◽  
...  
Keyword(s):  
Space Distribution ◽  
Background Intensity ◽  
Additional Contribution ◽  
List Type ◽  
X Ray ◽  
Upper Limit ◽  
Angular Scale ◽  
Sky Survey ◽  
The Mean ◽  
X Ray Background

Studies of the HEAO–1 A2 all–sky survey data have established that the level of anisotropy of the extragalactic X–ray background (XRB) is relatively low: –The cell–to–cell XRB intensity variations can be entirely accounted for by Poisson fluctuations in the space distribution of known classes of sources; the 90% confidence upper limit to any additional contribution on a scale of 26 square degrees is 2.3% (Shafer and Fabian 1983).–No significant correlations of XRB intensity fluctuations appear to be present; the formal 90% confidence upper limit on the amplitude of autocorrelations, relative to the mean background intensity, for an angular scale of 3° is Γ(3°) ≤ 1.9 × 10−2 (Persic et al. 1988).

scholarly journals The correlation function of the 4-12 keV X-ray background intensity measured with the GINGA LAC

1991 ◽  
Vol 249 (4) ◽  
pp. 698-703 ◽  
Author(s):  
F. J. Carrera ◽  
X. Barcons ◽  
J. A. Butcher ◽  
A. C. Fabian ◽  
G. C. Stewart ◽  
...  
Keyword(s):  
Correlation Function ◽  
Background Intensity ◽  
X Ray ◽  
X Ray Background

scholarly journals SPectral Observation of the Soft X-Ray Background and of the North Polar Spur with Solid State Spectrometers

1983 ◽  
Vol 101 ◽  
pp. 357-360
Author(s):  
R. Rocchia ◽  
M. Arnaud ◽  
C. Blondel ◽  
C. Cheron ◽  
J. C. Christy ◽  
...  
Keyword(s):  
Solid State ◽  
Solid Angle ◽  
Detection System ◽  
Field Of View ◽  
X Ray ◽  
The North ◽  
Diffuse Background ◽  
North Polar ◽  
X Ray Background ◽  
White Sands

In this paper, we present preliminary results of soft X-ray diffuse background observations. We observed two particular regions of the sky in the 0.3–1.5 keV range. The detection system consisted of three independent, 1 cm diameter, cooled solid state detectors. Nearly overlapping fields of view subtended a solid angle of approximately 1/4 sr. Except for the field of view, the whole set was similar to that described in Schnopper et al. (1982) (hereafter referred to as paper 1). This system was flown on board a three-axis stalibized rocket. The flight took place at White Sands Missile Range on 1981 May 4 at 0755 UT.

scholarly journals The Soft X-Ray Background

1973 ◽  
Vol 55 ◽  
pp. 215-234
Author(s):  
H. Friedman ◽  
G. Fritz ◽  
S. D. Shulman ◽  
R. C. Henry
Keyword(s):  
Background Radiation ◽  
Substantial Evidence ◽  
Interstellar Absorption ◽  
X Ray ◽  
Diffuse Background ◽  
X Ray Background

A survey of soft X-ray background observations in the 0.1–10 keV range is presented. In the region above 1 keV, recent results on point X-ray sources are discussed and their integrated contribution to the diffuse background is estimated. However, the average luminosity of various classes of extragalactic X-ray sources is still not sufficiently well known to permit this estimate to be made with any certainty. A discussion is given of recent observations at energies below 1 keV where the effects of interstellar absorption are important. It is argued that although some fraction of the background radiation in the 0.1–1 keV range must be galactic in origin, there is still substantial evidence for an extragalactic component. Proposed theories for generating both the galactic and extragalactic X-ray background are briefly reviewed.

scholarly journals Intergalactic Gas

1974 ◽  
Vol 63 ◽  
pp. 13-30
Author(s):  
George B. Field
Keyword(s):  
Background Intensity ◽  
Clusters Of Galaxies ◽  
Intergalactic Gas ◽  
X Ray ◽  
Direct Observations ◽  
X Ray Background ◽  
Intracluster Gas

Evidence that rich clusters of galaxies contain hot (T = 108 K) intracluster gas is reviewed. Such gas contributes little to Ω (0.003) but it has been argued that Ω must be less than 0.05 for true intergalactic gas, if accretion of more gas than is observed in rich clusters is to be avoided. This argument is reviewed.If the de Vaucouleurs' groups are bound by intracluster gas, T is expected to be 105 to 107 K and the contribution to Ω is ≃ 1. Since the clumping factor C is estimated to be ≃ 7, the resulting value of Ω2C is ≃ 7. This does not violate the observed diffuse soft X-ray background intensity. Gas should be sought in such groups. Smoothly distributed gas with 107 < T < 3 × 108 K and Ω = 1 is not ruled out by direct observations.

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