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 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 Modeling the Local Bubble

1997 ◽  
Vol 166 ◽  
pp. 121-131 ◽  
Author(s):  
Donald P. Cox
Keyword(s):  
Solar System ◽  
Facial Expressions ◽  
Simplified Model ◽  
Observational Constraints ◽  
Local Bubble ◽  
Interstellar Absorption ◽  
Modeling Effort ◽  
X Ray ◽  
Idealized Modeling ◽  
X Ray Background

AbstractModeling the Local Bubble is one of those activities fraught with danger. It is very easy to be too naive, to fail to consider the dependence of the model on assumptions about the nearby ambient state, or the likelihood of such a structure. It is similarly easy to become so caught up in the details of the vicinity that it is unclear where to begin a necessarily idealized modeling effort. And finally, it is important to remember that the data we have may in some cases be lying to us, and that we have not yet learned to read their facial expressions quite carefully enough.That said, I’ve tried in this paper to be helpful to those who may wish to take the risks. I surveyed the very most basic stories that the data seem to tell, and pointed out the standard coincidences that may be telling us a lot about what is happening, but may turn out once again to have been just coincidences. I’ve described 5 distinct conceptions that in one flavor or another pretty well survey the collection of mental images that have so far been carried by those who’ve attempted models. One may be right, or something entirely different may be more appropriate. It’s at least vital to realize that a conception comes first, followed by a simplified model of details. I’ve also included a long list of questions directed at observers. Some have partial answers, some one wouldn’t know today quite how to approach. But it is a list that students of the soft x-ray background, interstellar absorption lines, possible instrumentation, and the heliosphere may wish to review from time to time, just to see whether they can figure out how to be more helpful. There is another list for modelers, things the models must address, however-so-flimsily if necessary, because there are strong observational constraints (and stronger ones coming) on what can and cannot be present in the local ISM. To that I’ve added a few remarks concerning x-ray emission coming from beyond the Local Bubble, and another few on how x-ray emission from within the solar system might be contaminating what we see. That last bit is new, exciting, and possibly wrong, but it is an example of the ongoing wariness I believe one has to take toward the facts in the case. By the way, Dieter, it really was a great meeting.

scholarly journals The Microwave Background Radiation

1990 ◽  
Vol 139 ◽  
pp. 333-343 ◽  
Author(s):  
G. De Zotti ◽  
L. Danese ◽  
L. Toffolatti ◽  
A. Franceschini
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
High Redshift ◽  
Dust Emission ◽  
Radio Sources ◽  
Microwave Background ◽  
Satisfactory Explanation ◽  
X Ray ◽  
Microwave Background Radiation ◽  
X Ray Background

We review the data on the spectrum and isotropy of the microwave background radiation and the astrophysical processes that may produce spectral distortions and anisotropies. As yet no fully satisfactory explanation has been found for the submillimeter excess observed by Matsumoto et al. (1988). The most precise data at λ > 1 mm disagree with nonrelativistic comptonization models which match the excess. Distortions produced by a very hot intergalactic medium yielding the X-ray background do not fit the submillimeter data. Very special requirements must be met for the interpretation in terms of high-redshift dust emission to work.Reported anisotropies on scales of several degrees and of tens of arcsec may be produced, at least in part, by discrete sources. Because the best experiments at cm wavelengths are close to the confusion limit, they provide interesting information on the large-scale distribution of radio sources.

Origin of cosmic X-ray background radiation

1991 ◽  
Vol 378 ◽  
pp. L11 ◽  
Author(s):  
Nobuo Terasawa
Keyword(s):  
Background Radiation ◽  
X Ray ◽  
X Ray Background

X-Ray Astronomy

1969 ◽  
Vol 13 ◽  
pp. 289-312
Author(s):  
Herbert Friedman
Keyword(s):  
Radio Galaxy ◽  
Galactic Plane ◽  
Background Radiation ◽  
Galactic Latitude ◽  
Intergalactic Gas ◽  
High Galactic Latitude ◽  
X Ray ◽  
Diffuse Background ◽  
Distant Radio Galaxy ◽  
Radio Power

Although searches so far have been restricted to a few small rockets and balloons, some 40 discrete x-ray sources have already been resolved against a diffuse, nearly isotropic background radiation. The strongest source is about 2000 times as bright as the weakest detectable with present rocket instruments. Nearly all of the discrete sources lie close to the galactic plane and most likely are members of the spiral arms of the Milky Way. One x-ray source at high galactic latitude is identifiable with a distant radio galaxy, Virgo A, and its x-ray luminosity is 70 times its radio power. The diffuse background radiation seems to be resolvable into at least two components: one may be associated with the interaction of cosmic rays and the microwave photons of the cosmological 3 K background; the other with bremsstrahlung from hot, intergalactic gas.

scholarly journals The Cosmic Background Radiation: Some Recent Developments

1971 ◽  
Vol 2 ◽  
pp. 757-767
Author(s):  
M. J. Rees
Keyword(s):  
Background Radiation ◽  
Cosmic Background Radiation ◽  
Galactic Disc ◽  
Yield Data ◽  
X Ray ◽  
Cosmic Background ◽  
Upper Limits ◽  
Diffuse Background ◽  
The Galaxy ◽  
Recent Developments

Diffuse background radiation has been detected over 16 decades of frequency - from a few MHz up to ~3 × 1016 MHz (100 MeV) - and there are upper limits over an even wider range. Generally an important contribution comes from the galactic disc, but in some wavebands it has proved possible to isolate a truly cosmic isotropic component originating beyond our own Galaxy. A simple Olbers-type argument shows that the bulk of any extragalactic radiation field originates at cosmological distances. This is true whether the radiation is emitted by discrete sources, or comes from extragalactic (or pregalactic) space. Thus studies of the isotropie background radiation, or even upper limits to its intensity, yield data that are vital for cosmology, as well as telling us something about the properties of diffuse intergalactic matter, and about intrinsically faint extragalactic objects which cannot be observed individually.In this talk I shall not attempt a systematic review of this extensive subject, but will merely discuss a few recent developments. I shall give special attention to the microwave and X-ray regions of the spectrum, as these are the two bands in which the cosmic background is so strong that it swamps the emission from the Galaxy.

scholarly journals Primeval clusters of galaxies and the X-ray background

1978 ◽  
Vol 79 ◽  
pp. 445-446
Author(s):  
Edwin M. Kellogg
Keyword(s):  
Background Radiation ◽  
Active Galaxies ◽  
Point Sources ◽  
Clusters Of Galaxies ◽  
Sky Surveys ◽  
X Ray ◽  
Large Factor ◽  
X Ray Background

The X-ray telescope for HEAO-B, due for launch next year, will extend our observing power in X-ray astronomy by a very large factor. For example, its sensitivity to point sources will be 103 greater than the limit of existing X-ray sky surveys. Even more intriguing will be its capability to image the all-sky X-ray background radiation on an arc minute or sub arc minute scale. the origin of this background is still a mystery. the simplest hypothesis, that it is the integral of radiation from the more distant members of the classes of discrete X-ray sources such as clusters of galaxies, Seyferts, QSO's and other active galaxies, can only explain part of the 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.

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