The U.K. Deep and Medium Surveys with Rosat: log N-Log S relation

We have carried out a soft X-ray survey of the sky using the ROSAT Position Sensitive Proportional Counter (PSPC) in a region of very low Galactic column density (NH = 6–9 × 1019 cm–2). The data consist of a deep > 70 ks pointing (the Deep Survey) and six pointings at lower sensitivity (13–20 ks;...

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Detalhes bibliográficos
Autores: Branduardi-Raymont, G., Mason, Keith O., Warwick, R. S., Carrera, Francisco J., Graffagnino, V. G., Mittaz, J. P. D., Puchnarewicz, E. M., Smith, P. J., Barber, C. R., Pounds, K. A., Stewart, G. C., McHardy, I. M., Jones, L. R., Merrifield, M. R., Fabian, Andrew C., McMahon, Richard G., Ward, Martin J., George, I. M., Jones, M. H., Lawrence, A., Rowan-Robinson, Michael
Formato: artículo
Estado:Versión publicada
Fecha de publicación:1994
País:España
Recursos:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/170160
Acesso em linha:http://hdl.handle.net/10261/170160
Access Level:acceso abierto
Palavra-chave:Galaxies: active
X-ray general
Diffuse radiation
Descrição
Resumo:We have carried out a soft X-ray survey of the sky using the ROSAT Position Sensitive Proportional Counter (PSPC) in a region of very low Galactic column density (NH = 6–9 × 1019 cm–2). The data consist of a deep > 70 ks pointing (the Deep Survey) and six pointings at lower sensitivity (13–20 ks; the Medium Survey). We detect a total of 141 sources over the 0.9 deg2 of sky area used. The faintest source detected has a flux of 3.2 × 10–15 erg cm–2 s–1 (0.5–2.0 keV). We present the source number-flux distribution, and we compare it with the distributions constructed from other ROSAT observations and from surveys carried out with X-ray instruments operating at higher energies. We estimate the contribution of the resolved sources to the soft X-ray background by direct comparison of their integrated spectrum with that of the diffuse background: 44 per cent of the extragalactic X-ray background between 0.5 and 2.0 keV is resolved directly into discrete sources whose average spectrum is steeper than that of the background. Integration of our number-flux relation to infinite flux produces a background resolved fraction of 44±565 per cent (0.5–2.0 keV). Limits on the slope of the log N–log S curve at very faint fluxes are set by the measured value of the X-ray background.

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