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Frontiers Of Space And Ground-Based Astronomy - The Astrophysics of the 21st Century (Hardcover, 1994 ed.)
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Frontiers Of Space And Ground-Based Astronomy - The Astrophysics of the 21st Century (Hardcover, 1994 ed.)
Series: Astrophysics and Space Science Library, 187
Expected to ship within 12 - 17 working days
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ROSAT Observations G. HASINGER Max-Planck-Institut flir
extraterrestrische Physik, D-85740 Garching, Germany Abstract. This
review describes the most recent advances in the study of the
extragalactic soft X-ray background and what we can learn about its
constituents. The deepest pointed observations with the ROSAT PSPC
are discussed. The logN-logS relation is presented, which reaches
to the faintest X-ray fluxes and to the highest AGN surface
densities ever achieved. The N(>S) relation shows a 2 density in
excess of 400 deg- at the faintest fluxes and a flattening below
the Einstein Deep Survey limit. About 60% of the extragalactic
background has been resolved in the deepest field. Detailed source
spectra and first optical and radio identifications will be
discussed. The results are put into perspective of the higher
energy X -ray background. Key words: X-rays, background radiations,
active galactic nuclei. 1. Introduction The extragalactic X-ray
background (XRB), discovered about 30 years ago, has been studied
extensively with many X-ray experiments, in particular with the
satel lites HEAO I and II (see ego Boldt 1987) and with ROSAT (e.
g. Hasinger et aI. , 1993). Figure 1 shows a compilation of some of
the most recent spectral measure ments for the X-ray background.
Over the energy range from 3 to about 100 keY its spectrum can be
well approximated by an optically thin thermal bremsstrahlung model
with kT ~ 40 keY, while at lower X-ray energies a steepening into a
new component has been observed observed (e. g.
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