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Por favor, use este identificador para citar o enlazar a este item: http://hdl.handle.net/10261/13012

The XMM-Newton serendipitous survey. IV. Optical identification of the XMM-Newton medium sensitivity survey (XMS)

AutorBarcons, Xavier ; Barcons, Xavier ; Carrera, Francisco J. ; Ceballos, María Teresa ; Bussons-Gordo, Javier; Corral, Amalia ; Ebrero, Jacobo ; Mateos, Silvia ; Panessa, Francesca ; Ullán, Aurora
Palabras claveX-rays: general
X-rays: galaxies
X-rays: stars
Galaxies: active
Fecha de publicacióndic-2007
EditorEDP Sciences
CitaciónAstronomy & Astrophysics 476(3): 1191-1203 (2007)
Resumen[Aims] X-ray sources at intermediate fluxes (a few x 10-14 erg cm-2 s-1) with a sky density of ~100 deg-2 are responsible for a significant fraction of the cosmic X-ray background at various energies below 10 keV. The aim of this paper is to provide an unbiased and quantitative description of the X-ray source population at these fluxes and in various X-ray energy bands.
[Methods] We present the XMM-Newton Medium sensitivity Survey (XMS), including a total of 318 X-ray sources found among the serendipitous content of 25 XMM-Newton target fields. The XMS comprises four largely overlapping source samples selected at soft (0.5-2 keV), intermediate (0.5-4.5 keV), hard (2-10 keV) and ultra-hard (4.5-7.5 keV) bands, the first three of them being flux-limited.
[Results] We report on the optical identification of the XMS samples, complete to 85-95%. At the flux levels sampled by the XMS we find that the X-ray sky is largely dominated by Active Galactic Nuclei. The fraction of stars in soft X-ray selected samples is below 10%, and only a few per cent for hard selected samples. We find that the fraction of optically obscured objects in the AGN population stays constant at around 15-20% for soft and intermediate band selected X-ray sources, over 2 decades of flux. The fraction of obscured objects amongst the AGN population is larger (~35-45%) in the hard or ultra-hard selected samples, and constant across a similarly wide flux range. The distribution in X-ray-to-optical flux ratio is a strong function of the selection band, with a larger fraction of sources with high values in hard selected samples. Sources with X-ray-to-optical flux ratios in excess of 10 are dominated by obscured AGN, but with a significant contribution from unobscured AGN.
Descripción30 páginas, 6 figuras, 7+5 tablas.-- et al.
Versión del editorhttp://dx.doi.org/10.1051/0004-6361:20077606
ISSN0004-6361 (Print)
1432-0746 (Online)
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