The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://dspace-roma3.caspur.it:80 2013-05-21T10:56:21Z 2013-05-21T10:56:21Z 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. http://hdl.handle.net/2307/293 2011-12-22T13:34:56Z 2009-09-30T22:00:00Z

<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