Soft X-Ray Background Flux

Bunner, A. N.; Coleman, Phaedra; Kraushaar, W. L.; McCammon, D.; Palmieri, T. M.; Shilepsky, A.; Ulmer, M. P.

doi:10.1038/2231222a0

Cited by 69 publications

(16 citation statements)

References 7 publications

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“…In the 3-10 keV band, this can be approximated by a power law with a photon index of À1.4. At energies below 1 keV, the background surface brightness exceeds the extrapolation of this power law (Bunner et al 1969). Later observations with gas scintillation proportional counters and solidstate detectors (Inoue et al 1979;Schnopper et al 1982;Rocchia et al 1984) suggested emission lines in the 0.5-1.0 keV band, most likely from oxygen.…”

Section: Introductionmentioning

confidence: 99%

ChandraSpectra of the Soft X‐Ray Diffuse Background

Markevitch

Bautz

Biller

et al. 2003

ApJ

164

170

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We present an exploratory Chandra ACIS-S3 study of the diffuse component of the cosmic X-ray background (CXB) in the 0.3-7 keV band for four directions at high Galactic latitudes, with emphasis on details of the ACIS instrumental background modeling. Observations of the dark Moon are used to model the detector background. A comparison of the Moon data and the data obtained with ACIS stowed outside the focal area showed that the dark Moon does not emit significantly in our band. Point sources down to 3 Â 10 À16 ergs s À1 cm À2 in the 0.5-2 keV band are excluded in our two deepest observations. We estimate the contribution of fainter, undetected sources to be less than 20% of the remaining CXB flux in this band in all four pointings. In the 0.3-1 keV band, the diffuse signal varies strongly from field to field and contributes between 55% and 90% of the total CXB signal. It is dominated by emission lines that can be modeled by a kT ¼ 0:1 0:4 keV plasma. In particular, the two fields located away from bright Galactic features show a prominent line blend at E % 580 eV (O vii+O viii) and a possible line feature at E $ 300 eV. The two pointings toward the North Polar Spur exhibit a brighter O blend and additional bright lines at 730-830 eV (Fe xvii). We measure the total 1-2 keV flux of 1:0 1:2 AE 0:2 ð Þ Â 10 À15 ergs s À1 cm À2 arcmin À2 (mostly resolved) and the 2-7 keV flux of 4:0 4:5 AE 1:5 ð Þ Â 10 À15 ergs s À1 cm À2 arcmin À2 . At E > 2 keV, the diffuse emission is consistent with zero, to an accuracy limited by the short Moon exposure and systematic uncertainties of the S3 background. Assuming Galactic or local origin of the line emission, we put an upper limit of $3 Â 10 À15 ergs s À1 cm À2 arcmin À2 on the 0.3-1 keV extragalactic diffuse flux.

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Section: Introductionmentioning

confidence: 99%

ChandraSpectra of the Soft X‐Ray Diffuse Background

Markevitch

Bautz

Biller

et al. 2003

ApJ

164

170

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“…The data do not seem to indicate a peak intensity at low to intermediate latitudes. This problem in fitting the latitude dependence at wavelengths shorter than 44 A was also noted by the Wisconsin group (Bunner et al, 1969) in attempting to fit their data in an energy region from 0.5-1.0 keV.…”

Section: Modelsmentioning

confidence: 96%

The Soft X-Ray Background

Friedman¹,

Fritz²,

Shulman³

et al. 1973

Symp. - Int. Astron. Union

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Abstract. 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 contri bution 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.

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“…The strength of the argument that this radiation is being generated by a process different from that of the remainder of the background depends, to a considerable extent, on how far above the extrapolation of a power law spectrum the corrected soft X-ray measurements lie. The most recent observations (Bunner et al, 1969) still show that there is great uncertainty, but they have measurements over a wide enough spectral range so that they conclude that either a steady-state density model with a temperature -3x 10 6 K (as discussed by Field and Henry) is compatible with the data, or an evolving model with T~ 10 6 K and Q G~Qc /6. It is also clear, as they and others have stressed, that discrete sources of soft X-rays, either in the halo of our Galaxy or on the extragalactic scale, might also explain the data.…”

Section: X-ray Observationsmentioning

confidence: 99%

Intergalactic Matter and Radiation

Burbidge

1972

Symp. - Int. Astron. Union

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Abstract. This paper presents a critical discussion of our present knowledge of intergalactic matter and radiation as it relates to cosmology. While there have been some observational successes and much theoretical speculation, studies of intergalactic matter and radiation have still not allowed us to draw certain conclusions about the origin and evolution of the universe.One of the most important quantities which we need to detect and understand from the point of observational cosmology is the total amount of matter and radiation in the universe. We are able to detect comparatively easily the discrete sources which emit electromagnetic radiation, but it would be very rash to assume that these are all that are present in the universe.Other components which may be present are: Knowledge of the relative importance of these different components can certainly be expected to increase our understanding (or, more appropriately, decrease our ignorance by a small amount) concerning the formation and evolution of galaxies and other condensed objects. If we could make a direct estimate of the total massenergy density of all of these components, Q C9 this could be directly used to restrict the possible cosmological models, the point being that, in the Friedman models and in the steady-state models, Q C is directly related to the other cosmological parameters H 0 , A, q 0 by the relations

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Soft X-Ray Background Flux

Cited by 69 publications

References 7 publications

ChandraSpectra of the Soft X‐Ray Diffuse Background

ChandraSpectra of the Soft X‐Ray Diffuse Background

The Soft X-Ray Background

Intergalactic Matter and Radiation

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