1998A&A...329..482H -
Astronomy and Astrophysics, volume 329, 482-494 (1998/1-2)
The ROSAT Deep Survey. I. X-ray sources in the Lockman Field.
HASINGER G., BURG R., GIACCONI R., SCHMIDT M., TRUEMPER J. and ZAMORANI G.
Abstract (from CDS):
The ROSAT Deep Survey in the Lockman Hole is the most sensitive X-ray survey performed to date, encompassing an exposure time of 207ksec with the PSPC and a total of 1.32Msec with the HRI aboard ROSAT. Here we present the complete catalogue of 50 X-ray sources with PSPC fluxes (0.5-2keV) above 5.5x10–15erg/cm2/s. The optical identifications are discussed in an accompanying paper (Schmidt et al., 1997). We also derive a new log(N)-log(S) function reaching a source density of 970±150deg–2 at a limiting flux of 10–15erg/cm2/s. At this level 70-80% of the 0.5-2keV X-ray background is resolved into discrete sources. Utilizing extensive simulations of artificial PSPC and HRI fields we discuss in detail the effects of source confusion and incompleteness both on source counts and on optical identifications. Based on these simulations we set conservative limits on flux and on off-axis angles, which guarantee a high reliability of the catalogue. We also present simulations of shallower fields and show that surveys, which are based on PSPC exposures longer than 50ksec, become severely confusion limited typically a factor of 2 above their 4σ detection threshold. This has consequences for recent claims of a possible new source population emerging at the faintest X-ray fluxes.
Abstract Copyright:
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Journal keyword(s):
surveys - cosmology: diffuse radiations - X-rays: galaxies
VizieR on-line data:
<Available at CDS (J/A+A/329/482): table4.dat>
Nomenclature:
Table 4: RDS NNN N=50 among about 960
Simbad objects:
50
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