Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 2007 | Published
Journal Article Open

The XMM-Newton Wide-Field Survey in the COSMOS Field. IV. X-Ray Spectral Properties of Active Galactic Nuclei


We present a detailed spectral analysis of pointlike X-ray sources in the XMM-NewtonCOSMOS field. Our sample of 135 sources only includes those that have more than 100 net counts in the 0.3-10 keV energy band and have been identified through optical spectroscopy. The majority of the sources are well described by a simple power-law model with either no absorption (76%) or a significant intrinsic, absorbing column (20%). The remaining ~4% of the sources require a more complex modeling by incorporating additional components to the power law. For sourceswith more than 180 net counts (bright sample), we allowed both the photon spectral index Γ and the equivalent hydrogen column N_H to be free parameters. For fainter sources, we fix Γ to the average value and allow N_H to vary. The mean spectral index of the 82 sources in the bright sample is <Γ> = 2:06 ± 0:08, with an intrinsic dispersion of ~0.24. Each of these sources has fractional errors on the value of Γ below 20%. As expected, the distribution of intrinsic absorbing column densities is markedly different between AGNs with or without broad optical emission lines. We find within our sample four type 2 QSO candidates (L_X >10^(44) ergs s^(-1), N_H >10^(22) cm^(-2)), with a spectral energy distribution well reproduced by a composite Seyfert 2 spectrum, that demonstrates the strength of the wide-field COSMOS XMM-Newton survey to detect these rare and underrepresented sources. In addition, we have identified a Compton-thick (N_H >1:5 ; 10^(24) cm^(-)2) AGN at z = 0:1248. Its X-ray spectrum is well fitted by a pure reflection model and a significant Fe Kα line at rest-frame energy of 6.4 keV.

Additional Information

© 2007 The American Astronomical Society. Received 2006 April 24; accepted 2006 December 5. This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the US (NASA). In Germany, the XMM-Newton project is supported by the Bundesministerium fu¨r Wirtschaft und Technologie/Deutsches Zentrum fu¨r Luft- und Raumfahrt (BMWI/DLR, FKZ 50 OX 0001), the Max-Planck Society and the Heidenhain-Stiftung. Part of this work was supported by the Deutsches Zentrum fu¨ r Luft- und Raumfahrt, DLR project numbers 50 OR 0207 and 50 OR 0405. In Italy, the COSMOS XMM-Newton project is supported by INAF and MIUR under grants PRIN/270/2003 and Cofin-03-02-23. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. The HST COSMOS Treasury program was supported through NASA grant HST-GO-09822. Also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the European Southern Observatory under Large Program 175.A-0839, Chile; and the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We are grateful to Paolo Tozzi, Kazushi Iwasawa, and Paolo Padovani for inspiring discussions. We gratefully acknowledge the entire COSMOS collaboration consisting of more than 70 scientists. More information on the COSMOS survey is available at http://www.astro.caltech.edu/_cosmos. It is a pleasure the acknowledge the excellent services provided by the NASA IPAC/IRSA staff (Anastasia Laity, Anastasia Alexov, Bruce Berriman, and John Good) in providing online archive and server capabilities for the COSMOS data sets.

Attached Files

Published - MAIapjss07.pdf


Files (937.9 kB)
Name Size Download all
937.9 kB Preview Download

Additional details

August 22, 2023
October 19, 2023