scholarly journals The X-ray properties of high redshift quasi-stellar objects

1986 ◽  
Vol 119 ◽  
pp. 247-252
Author(s):  
Scott F. Anderson ◽  
Bruce Margon
Keyword(s):  
Background Radiation ◽  
High Redshift ◽  
Galactic Latitude ◽  
X Rays ◽  
Stellar Objects ◽  
High Galactic Latitude ◽  
X Ray ◽  
Quasi Stellar Objects ◽  
X Ray Background ◽  
Intermediate Redshift

We describe a program aimed at characterizing the X-ray emission of high redshift QSOs. We have obtained slitless spectra of 50 high galactic latitude fields previously imaged at very high levels of sensitivity by the Einstein Observatory, generally for original goals unrelated to QSOs. Our survey, covering ∼ 17 deg2 of sky to limiting magnitude Bcont ∼ 21, has yielded ∼ 400 previously uncatalogued QSO candidates, each with sensitive new X-ray information available. About 100 of these objects, constituting a “high confidence” set of QSOs, chiefly in the redshift range 1.7 < z < 3 and thus complementary to previous samples with X-ray data, are used to derive the X-ray properties of high redshift QSOs. Even at these most sensitive available X-ray flux levels, only about 25% of the objects are positively detected in X-rays; thus extensive attention has been given to proper treatment of the upper-limit information. We find a mean optical-to-X-ray slope parameter for the sample of . Our results are combined with those of previous surveys to estimate the fraction of the diffuse X-ray background radiation due to QSOs. QSOs are capable of supplying the majority of the radiation, but the chief contribution comes from an annulus of intermediate redshift, moderate luminosity objects.

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.

The X-ray properties of high-redshift quasi-stellar objects

1987 ◽  
Vol 314 ◽  
pp. 111 ◽  
Author(s):  
Scott F. Anderson ◽  
Bruce Margon
Keyword(s):  
High Redshift ◽  
Stellar Objects ◽  
X Ray ◽  
Quasi Stellar Objects

scholarly journals The X-ray Spectra of High Redshift Quasars

1989 ◽  
Vol 134 ◽  
pp. 161-166
Author(s):  
Claude R. Canizares ◽  
Julia L. White
Keyword(s):  
High Redshift ◽  
Radio Spectrum ◽  
Clear Correlation ◽  
X Rays ◽  
Spectral Parameters ◽  
X Ray ◽  
Systematic Uncertainties ◽  
Two Component ◽  
X Ray Background ◽  
Single Power

We present mean spectral parameters for various ensembles of quasars observed with the Einstein Observatory Imaging Proportional Counter (IPC). Our sample contains 71 optically or radio selected quasars with 0.1 < z < 3.5, Galactic NH < 1021 cm−2, total counts of 30 −500, and IPC gain < 19. Quasars are grouped into ensembles according to radio properties (Flat Radio Spectrum [FRS], Steep Radio Spectrum [SRS] or Radio Quiet [RQ]), and either redshift or X-ray luminosity, lx. We find a clear correlation between radio properties and α. FRS quasars have α∼0.4, SRS quasars have α∼0.7 and RQ quasars have α ∼1–1.4. There is no evidence for a dependence of α on z nor, for the FRS and SRS ensembles, on lx over nearly three decades. FRS quasars with 2.0 < z < 3.5 have just as flat mean spectra as those with low z, implying that a single power law, which is flatter than the canonical one with α ∼ 0.65, continues into the 1–10 keV band (in which the observed softer X-rays were emitted). Unfortunately, the results for high redshift and high lx RQ quasars are ambiguous because of systematic uncertainties in the ensemble means. Thus we cannot test the two-component spectral hypothesis of Wilkes and Elvis for these objects. SRS X-ray spectra could be steeper than FRS spectra because of the mixing of two components, although a single intrinsically steeper spectrum is easier to reconcile with the absence of z dependence. The uncertainty in a for RQ quasars with high z leaves open the important question of their contribution to the cosmic X-ray background.

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.

scholarly journals ASCA Sky Survey Observations and the Cosmic X-Ray Background in 2-10 KeV

1998 ◽  
Vol 188 ◽  
pp. 197-200
Author(s):  
H. Inoue ◽  
T. Takahashi ◽  
Y. Ueda ◽  
A. Yamashita ◽  
Y. Ishisaki ◽  
...  
Keyword(s):  
Energy Range ◽  
Galactic Plane ◽  
Galactic Latitude ◽  
High Galactic Latitude ◽  
X Ray ◽  
Sky Survey ◽  
X Ray Background ◽  
Excess Component ◽  
Highly Uniform

The X-ray background in the energy range above 2 keV is highly uniform except for an excess component along the Galactic plane. The excess along the plane is considered to be associated with our Galaxy, whereas the rest of the emission is believed to be of extragalactic origin. In this paper, the X-ray background at high Galactic latitude is discussed and is designated as the CXB (cosmic X-ray background) to distinguish it from the Galactic origin.

Ariel results on extragalactic X-ray sources

1976 ◽  
Vol 350 (1663) ◽  
pp. 491-503 ◽  
Keyword(s):  
High Latitude ◽  
Field Of View ◽  
Potential Contribution ◽  
Galactic Latitude ◽  
Survey Experiment ◽  
Spectral Measurements ◽  
High Galactic Latitude ◽  
X Ray ◽  
X Ray Background ◽  
The University

Two of the instruments on Ariel 5 are designed to study the weak high galactic latitude X-ray sources, a number of which have been identified with extragalactic objects. The survey experiment of the University of Leicester has detected sources with strengths down to 2-3 Uhuru counts. Several high latitude sources catalogued by Uhuru have apparently dropped in intensity below this level and improved positions have been obtained for other high latitude sources which support the tentative identification with optical counterparts. The pointed instrument from M. S. S. L. has a programme of spectral measurements of identified extragalactic and other weak sources at high galactic latitudes. The field of view of the M. S. S. L. experiment makes the instrument well suited to the study of the diffuse X-ray background. Results are presented from both experiments on a number of the extragalactic sources and, in particular, discussed in relation to their potential contribution to the diffuse X-ray background. Preliminary measurements of the diffuse X-ray background by the M. S. S. L. instruments are presented.

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 Local Contributions to the 0.6 keV Diffuse X-Ray Background

1984 ◽  
Vol 81 ◽  
pp. 215-218 ◽  
Author(s):  
David N. Burrows
Keyword(s):  
Galactic Latitude ◽  
The Sun ◽  
X Rays ◽  
Diffuse Emission ◽  
General Direction ◽  
X Ray ◽  
Hot Gas ◽  
X Ray Background

The intensity of the X-ray background between 0.5 and 1.0 keV has surprisingly little dependence on galactic latitude. Possible mechanisms for the production of these X-rays include extragalactic emission and emission from dM stars, both of which should be strongly dependent on galactic latitude, and diffuse emission from hot gas (T ≃ 3 x 106 K) surrounding the Sun. These mechanisms can be distinguished by the presence or absence of absorption by gas within a few hundred parsecs of the Sun. We use X-ray data from the HEA0-1 LED detectors and HI data from the recent Crawford Hill 21 cm survey to place limits on the 0.6 keV intensity originating within 300 pc of the Sun in the general direction of (l,b) = (150°, -30°).

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