The X-Ray Background and the Space Distribution of QSOs

X-ray Constraints on AGN Clustering

Symposium - International Astronomical Union ◽

10.1017/s0074180900141798 ◽

1989 ◽

Vol 134 ◽

pp. 492-493

Author(s):

G. De Zotti ◽

M. Persic ◽

A. Franceschini ◽

L. Danese ◽

G.G.C. Palumbo ◽

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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).

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The Fluctuations of the Cosmic X-Ray Background as a Sensitive Tool to the Universal Source Distribution

Symposium - International Astronomical Union ◽

10.1017/s007418090007474x ◽

1981 ◽

Vol 94 ◽

pp. 277-278

Author(s):

P. Giommi ◽

G. F. Bignami

Keyword(s):

Low Energy ◽

Experimental Results ◽

Space Distribution ◽

Source Distribution ◽

X Ray ◽

Definite Relation ◽

Sensitive Tool ◽

X Ray Background ◽

Flux Curve

Recent experimental results (Giacconi et al, 79, Tananbaum et al 79) ascribe an increasingly important role to the contribution of discrete sources to the low-energy (few Kev) cosmic X-ray background (CXB). While the astrophysical nature of the objects involved is not yet clear, distant and powerful emitters like QSO play probably an important role (e.g. Setti and Woltjer 1979, Field 1980). For them, often the number-flux curve (LogN-LogS) provides useful hints on such properties as space distribution and/or evolution. For the case of the X-ray sources, moreover, a definite relation exists between their LogN-LogS and the granularity of the sky emission as described by the fluctuations of the X-ray background.

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Crystal truncation rod X-ray scattering: exact dynamical calculation

Journal of Applied Crystallography ◽

10.1107/s0021889807049886 ◽

2008 ◽

Vol 41 (1) ◽

pp. 18-26 ◽

Cited By ~ 8

Author(s):

Václav Holý ◽

Paul F. Fewster

Keyword(s):

Reciprocal Lattice ◽

Dynamical Theory ◽

Lattice Points ◽

Space Distribution ◽

Matrix Formalism ◽

X Ray ◽

Transmission Coefficients ◽

X Ray Scattering ◽

Crystal Truncation Rod ◽

Scattering Geometry

A new method is presented for a calculation of the reciprocal-space distribution of X-ray diffracted intensity along a crystal truncation rod. In contrast to usual kinematical or dynamical approaches, the method is correct both in the reciprocal-lattice points and between them. In the method, the crystal is divided into a sequence of very thin slabs parallel to the surface; in contrast to the well known Darwin dynamical theory, the electron density in the slabs is constant along the surface normal. The diffracted intensity is calculated by a matrix formalism based on the Fresnel reflection and transmission coefficients. The method is applicable for any polarization of the primary beam and also in a non-coplanar scattering geometry.

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