XMM-Newton observation of the Chandra Deep Field-South: statistical treatment of faint source spectra

Streblyanska, A.; Bergeron, J.; Brunner, H.; Finoguenov, A.; Hasinger, G.; Mainieri, V.
Referencia bibliográfica

Nuclear Physics B Proceedings Supplements, Volume 132, p. 232-235.

Fecha de publicación:
6
2004
Número de autores
6
Número de autores del IAC
0
Número de citas
14
Número de citas referidas
12
Descripción
We present first results of the X-ray spectral analysis of 500 ksec deep survey images obtained with XMM-Newton on the Chandra Deep Field South (CDFS). Statistical distributions of spectral index and intrinsic absorption are derived for a sample containing 70 sources with a count limit of 100 (flux limit in the 2-10 keV band of 8.9×10-16 erg cm-2s-1), of which 44 sources have had redshifts identified. We observe a spatial separation between the type-1 and the type-2 AGN in diagnostics involving different X-ray parameters. Using the subsample with known z, we show that this separation between the AGN populations is a consequence of different absorption column densities. The two populations have the same average spectral index, <Γ>=2+/-0.1. We present integrated spectra for the most distant type-2 QSO which shows strong X-ray absorption and a clear soft excess; we obtained the best fit for this object with a scattering model. We also confirm a progressive hardening for the combined integral spectra for faint objects which at first was noted by [Proceedings of the XXI Moriond Astrophysics Meeting (2001)]. Our results show a clear evolution of decrease of <Γ> with decreasing flux in the hard 2-10 keV band. However, we detect not only a regular increase in <Γ> for different subsamples of fluxes compared to Chandra results, but also a discrepancy of the values within our own data set, if we fitted in the different energy bands.