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THE LARGE-SCALE SURFACE BRIGHTNESS DISTRIBUTION OF THE X-RAY BACKGROUND
Pages 285-296

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From page 285...
... However, because of its relative uniformity (Schwartz and Gursky 1974; Schwartz 1979; Turner and Geller 1980) its seems fairly clear that the bunk of the E > 2 keV background is also of "cosmological" origin (e.g., due to objects or truly diffuse radiation originating at z > 0.~)
From page 286...
... The X-ray sources tend to be much more distant and have fainter optical counterparts. In addition, the X-ray source counts at high latitutde will be dominated by active galaxies rather than the star forming galaxies which dominate the IRAS counts.
From page 287...
... However the relative amplitude compared lo the micro-wave dipole term is expected to be small, < 0.6, for reasonable (bM < 102° solar masses on scales Liz ~ 1) , large-scale perturbations.
From page 288...
... Thus beam sizes of > 75 square degrees are necessary to examine surface brightness variations of < 2% with the HEAD-1 data. Galactic Component Previous studies using this data base (Shafer 1983; Twan et al.
From page 289...
... This region has an enhancement of ~ 4-5% of the average sky flux (^IGA ~ 7.8 x 10-~3 ergs/cm2sec/deg2, Jahoda and Mushotzly 1989) and subtends a solid angle of ~ 1,000 square degrees for a total flux of ~ 10-9 ergs/cm2-sec.
From page 290...
... This raises the interesting question of whether other superclusters are similar to the GA in being composed primarily of "field" galaxies and poor groups and has important implications for studies of large-scale structures. If the X-ray surface bnghmess enhancement detected in the region of the GA is due to hot gas located in the potential well of the supercluster we may estimate its core mass as: M(gas)
From page 291...
... (1989b) have used the same data base to place tight upper limits on diffuse radiation from optically selected "pointlike" superclusters (e.g., they have assumed that the superclusters were of angular size < 2°~.
From page 292...
... shows that most of the large-scale structure (other than in the GA regions is not directly assignable to the local supercluster. At the present time we do not know the physical origin of these "lumps," whether they are due to galactic or extragalactic effects or their possible relationship to other astrophysical objects.
From page 293...
... The major uncertainty was due to emission from the much larger galactic component, the small number of independent sky elements due to the dominance of sky fluctuation noise and the lack of information about structures like the GO Boldt (1987) gives a nice graphic representation of the problem.
From page 295...
... X-ray Astronomy NATO Advance Study Institutes Series. Scaramella et al.
From page 296...
... Puma Stan.


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