http://dspace-roma3.caspur.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-05-25T17:11:52Z http://hdl.handle.net/2307/293 <Title>Spectroscopy identifications of Spitzer sources in the SWIRE/XMM-Newton/ELAIS-S1 field : a large fraction of active galactic nuclei with high F(24 mu m)/F(R) ratio</Title> <Authors>Sacchi, Nicola; La Franca, Fabio; Feruglio, Chiara; Fiore, Fabrizio; Puccetti, Simonetta; Cocchia, Filomena; Berta, Stefano; Brusa, Marcella; Cimatti, Andrea; Comastri, Andrea; Franceschini, Alberto; Gruppioni, Carlotta; Maiolino, Roberto; Matute, Israel; Polletta, Maria; Pozzetti, Lucia; Pozzi, Francesca; Vignali, Cristian; Zamorani, Giovanni; Oliver, Seb; Rowan-Robinson, Michael; Smith, Gene; Lonsdale, Colin J.</Authors> <Issue Date>2009-10-01</Issue Date> <Is part of>Astrophysical Journal</Is part of> <Volume>703</Volume> <Pages>1778-1790</Pages> <Abstract>We present a catalog of optical spectroscopic identifications of sources detected by Spitzer at 3.6 or 24 mu m down to similar to 10 and similar to 280 mu Jy, respectively, in the SWIRE/XMM-Newton/ELAIS-S1 field and classified via line width analysis and diagnostic diagrams. A total of 1376 sources down to R similar to 24.2 mag have been identified (1362 detected at 3.6 mu m, 419 at 24 mu m, and 405 at both) by low-resolution optical spectroscopy carried out with FORS2, VIMOS, and EFOSC2 at the Very Large Telescope and 3.6 m ESO telescope. The spectroscopic campaigns have been carried out over the central 0.6deg(2) area of ELAIS-S1 which, in particular, has also been observed byXMM-Newton and Chandra. We find the first direct optical spectroscopic evidence that the fraction of active galactic nuclei (AGNs; mostlyAGN2) increases with increasing F(24 mu m)/F(R) ratio, reaching values of 70(+/- 20)% in the range 316 < F(24 mu m)/F(R) < 1000. We present an Infrared Array Camera - Multiband Imaging Photometer color - color diagram able to separate AGN1 from obscured AGN2 candidates. After having corrected for the spectroscopic incompleteness of our sample, the result is that the AGN fraction at F(24 mu m) similar to 0.8 mJy is similar to 22(+/- 7)% and decreases slowly to similar to 19(+/- 5)% down to F(24 mu m) similar to 0.3 mJy.</Abstract> 2009-09-30T22:00:00Z http://hdl.handle.net/2307/276 <Title>The HELLAS2XMM survey - XII. The infrared/submillimetre view of anX-ray selected type 2 quasar at z approximate to 2</Title> <Authors>Vignali, Cristian; Pozzi, Francesca; Fritz, Jacopo; Comastri, Andrea; Gruppioni, Carlotta; Bellocchi, Enrica; Fiore, Fabrizio; Brusa, Marcella; Maiolino, Roberto; Mignoli, Marco; La Franca, Fabio; Pozzetti, Lucia; Zamorani, Giovanni; Merloni, Andrea</Authors> <Issue Date>2009</Issue Date> <Is part of>MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY</Is part of> <Volume>395</Volume> <Pages>2189-2195</Pages> <Abstract>We present multiwavelength observations (from optical to submillimetre,including Spitzer and Submillimetre Common-User Bolometer Array) ofH2XMMJ003357.2-120038 (also GD158_19), an X-ray selected, luminousnarrow-line (type 2) quasar at z = 1.957 selected from the HELLAS2XMMsurvey. Its broad-band properties can be reasonably well modelledassuming three components: a stellar component to account for theoptical and near-infrared (IR) emission; an active galactic nucleus(AGN) component (i.e. dust heated by an accreting active nucleus),dominant in the mid-IR, with an optical depth at 9.7 mu m along theline of sight ( close to the equatorial plane of the obscuring matter)of tau(9.7) = 1 and a full covering angle of the reprocessing matter(torus) of 140 degrees and a far-IR starburst component (i.e. dustheated by star formation) to reproduce the wide bump observed longwardof 70 mu m.The derived star formation rate is approximate to 1500M(circle dot)yr(-1). The overall modelling indicates that GD158_19 is ahigh-redshift X-ray luminous, obscured quasar with coeval powerful AGNactivity and intense star formation. It is probably caught before theprocess of expelling the obscuring gas has started, thus quenching thestar formation.</Abstract> 2008-12-31T23:00:00Z