Please use this identifier to cite or link to this item: 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
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.
Keywords: AREA ISO SURVEY
X-RAY SOURCES
SPECTRAL ENERGY-DISTRIBUTIONS
ULTRALUMINOUS INFRARED GALAXIES
EXTRAGALACTIC SURVEY ESIS
DUST-OBSCURED GALAXIES
COMPTON-THICK QUASARS
STAR-FORMING GALAXIES
XMM-NEWTON SURVEY
15 MU-M
Issue Date: 1-Oct-2009
Publisher: IOP Publishing
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.
URI: http://hdl.handle.net/2307/293
ISSN: 0004-637X
DOI: 10.1088/0004-637X/703/2/1778
Appears in Collections:A - Articolo su rivista
X_Dipartimento di Fisica 'Edoardo Amaldi'

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