We report the final optical identifications of the medium-depth (∼60 ks), contiguous (2 deg2) XMM-Newton survey of the COSMOS field. XMM-Newton has detected ∼1800 X-ray sources down to limiting fluxes of ∼5 × 10−16, ∼3 × 10−15, and ∼7 × 10−15 erg cm−2 s−1 in the 0.5–2 keV, 2–10 keV, and 5–10 keV bands, respectively (∼1 × 10−15, ∼6 × 10−15, and ∼1 × 10−14 erg cm−2 s−1, in the three bands, respectively, over 50% of the area). The work is complemented by an extensive collection of multiwavelength data from 24 μm to UV, available from the COSMOS survey, for each of the X-ray sources, including spectroscopic redshifts for 50% of the sample, and high-quality photometric redshifts for the rest. The XMM and multiwavelength flux limits are well matched: 1760 (98%) of the X-ray sources have optical counterparts, 1711 (∼95%) have IRAC counterparts, and 1394 (∼78%) have MIPS 24 μm detections. Thanks to the redshift completeness (almost 100%) we were able to constrain the high-luminosity tail of the X-ray luminosity function confirming that the peak of the number density of log LX > 44.5 active galactic nuclei (AGNs) is at z ∼ 2. Spectroscopically identified obscured and unobscured AGNs, as well as normal and star-forming galaxies, present well-defined optical and infrared properties. We devised a robust method to identify a sample of ∼150 high-redshift (z > 1), obscured AGN candidates for which optical spectroscopy is not available. We were able to determine that the fraction of the obscured AGN population at the highest (LX > 1044 erg s−1) X-ray luminosity is ∼15%–30% when selection effects are taken into account, providing an important observational constraint for X-ray background synthesis. We studied in detail the optical spectrum and the overall spectral energy distribution of a prototypical Type 2 QSO, caught in a stage transitioning from being starburst dominated to AGN dominated, which was possible to isolate only thanks to the combination of X-ray and infrared observations.
The XMM-Newton Wide-Field Survey in the COSMOS field (XMM-COSMOS): demography and multiwavelength properties of obscured and unobscured luminous AGN / Brusa M.; Civano F.; Comastri A.; Miyaji T.; Salvato M.; Zamorani G.; Cappelluti N.; Fiore F.; Hasinger G.; Mainieri V.; Merloni A.; Bongiorno A.; Capak P.; Elvis M.; Gilli R.; Hao H.; Jahnke K.; Koekemoer A. M.; Ilbert O.; Le Floc'h E.; Lusso E.; Mignoli M.; Schinnerer E.; Silverman J. D.; Treister E.; Trump J. D.; Vignali C.; Zamojski M.; Aldcroft T.; Aussel H.; Bardelli S.; Bolzonella M.; Cappi A.; Caputi K.; Contini T.; Finoguenov A.; Fruscione A.; Garilli B.; Impey C. D.; Iovino A.; Iwasawa K.; Kampczyk P.; Kartaltepe J.; Kneib J. P.; Knobel C.; Kovac K.; Lamareille F.; Leborgne J.-F.; Le Brun V.; Le Fevre O.; Lilly S. J.; Maier C.; McCracken H. J.; Pello R.; Peng Y-J; Perez-Montero E.; de Ravel L.; Sanders D.; Scodeggio M.; Scoville N. Z.; Tanaka M.; Taniguchi Y.; Tasca L.; de la Torre S.; Tresse L.; Vergani D.; Zucca E.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 716:(2010), pp. 348-369. [10.1088/0004-637X/716/1/348]
The XMM-Newton Wide-Field Survey in the COSMOS field (XMM-COSMOS): demography and multiwavelength properties of obscured and unobscured luminous AGN
BRUSA, MARCELLA;LUSSO, ELISABETA;VIGNALI, CRISTIAN;
2010
Abstract
We report the final optical identifications of the medium-depth (∼60 ks), contiguous (2 deg2) XMM-Newton survey of the COSMOS field. XMM-Newton has detected ∼1800 X-ray sources down to limiting fluxes of ∼5 × 10−16, ∼3 × 10−15, and ∼7 × 10−15 erg cm−2 s−1 in the 0.5–2 keV, 2–10 keV, and 5–10 keV bands, respectively (∼1 × 10−15, ∼6 × 10−15, and ∼1 × 10−14 erg cm−2 s−1, in the three bands, respectively, over 50% of the area). The work is complemented by an extensive collection of multiwavelength data from 24 μm to UV, available from the COSMOS survey, for each of the X-ray sources, including spectroscopic redshifts for 50% of the sample, and high-quality photometric redshifts for the rest. The XMM and multiwavelength flux limits are well matched: 1760 (98%) of the X-ray sources have optical counterparts, 1711 (∼95%) have IRAC counterparts, and 1394 (∼78%) have MIPS 24 μm detections. Thanks to the redshift completeness (almost 100%) we were able to constrain the high-luminosity tail of the X-ray luminosity function confirming that the peak of the number density of log LX > 44.5 active galactic nuclei (AGNs) is at z ∼ 2. Spectroscopically identified obscured and unobscured AGNs, as well as normal and star-forming galaxies, present well-defined optical and infrared properties. We devised a robust method to identify a sample of ∼150 high-redshift (z > 1), obscured AGN candidates for which optical spectroscopy is not available. We were able to determine that the fraction of the obscured AGN population at the highest (LX > 1044 erg s−1) X-ray luminosity is ∼15%–30% when selection effects are taken into account, providing an important observational constraint for X-ray background synthesis. We studied in detail the optical spectrum and the overall spectral energy distribution of a prototypical Type 2 QSO, caught in a stage transitioning from being starburst dominated to AGN dominated, which was possible to isolate only thanks to the combination of X-ray and infrared observations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
