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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

2011-12-22T13:34:56Z

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 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. 2009-10-01 Astrophysical Journal 703 1778-1790 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.

How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582

2011-12-22T13:35:27Z

How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582 Bianchi, Stefano; Piconcelli, Enrico; Chiaberge, Marco; Jimenez Bailon, Elena; Matt, Giorgio; Fiore, Fabrizio 2009-04 Astrophysical Journal 695 781-787 We present the results of a Suzaku monitoring campaign of the Seyfert 2galaxy, NGC 7582. The source is characterized by very rapid (ontimescales even lower than a day) changes of the column density of aninner absorber, together with the presence of constant componentsarising as reprocessing from a Compton-thick material. The best-fittingscenario implies important modifications to the zeroth-order view ofUnified Models. While the existence of a pc-scale torus is needed inorder to produce a constant Compton reflection component and an ironKa-emission line, in this Seyfert 2 galaxy this is not viewed along theline of sight. On the other hand, the absorption of the primarycontinuum is due to another material, much closer to the black hole,roughly at the distance of the broad-line region, which can produce theobserved rapid spectral variability. On top of that, the constantpresence of a 10(22) cm(-2) column density can be ascribed to thepresence of a dust lane, extended on a galactic scale, as previouslyconfirmed by Chandra. There is now mounting evidence that complexity inthe obscuration of active galactic nuclei (AGNs) may be the rule ratherthan the exception. We therefore propose to modify the UnificationModel, adding to the torus the presence of two furtherabsorbers/emitters. Their combination along the line of sight canreproduce all the observed phenomenology.

The HELLAS2XMM survey - XII. The infrared/submillimetre view of anX-ray selected type 2 quasar at z approximate to 2

2011-12-22T13:35:27Z

The HELLAS2XMM survey - XII. The infrared/submillimetre view of anX-ray selected type 2 quasar at z approximate to 2 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 2009 MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 395 2189-2195 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.