The XMM-Newton wide-field survey in the COSMOS field. IV. X-ray spectral properties of active galactic nuclei

V. Mainieri, G. Hasinger, N. Cappelluti, M. Brusa, H. Brunner, F. Civano, A. Comastri, M. Elvis, A. Finoguenov, F. Fiore, R. Gilli, I. Lehmann, J. Silverman, L. Tasca, C. Vignali, G. Zamorani, E. Schinnerer, C. Impey, J. Trump, S. LillyC. Maier, R. E. Griffiths, T. Miyaji, P. Capak, A. Koekemoer, N. Scoville, P. Shopbell, Y. Taniguchi

Research output: Contribution to journalArticle

86 Scopus citations

Abstract

We present a detailed spectral analysis of pointlike X-ray sources in the XMM-Newton COSMOS 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 sources with 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 T 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.

Original languageEnglish (US)
Pages (from-to)368-382
Number of pages15
JournalAstrophysical Journal, Supplement Series
Volume172
Issue number1
DOIs
StatePublished - 2007

Keywords

  • Galaxies: active
  • Surveys
  • X-rays: diffuse background
  • X-rays: galaxies
  • X-rays: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Mainieri, V., Hasinger, G., Cappelluti, N., Brusa, M., Brunner, H., Civano, F., Comastri, A., Elvis, M., Finoguenov, A., Fiore, F., Gilli, R., Lehmann, I., Silverman, J., Tasca, L., Vignali, C., Zamorani, G., Schinnerer, E., Impey, C., Trump, J., ... Taniguchi, Y. (2007). The XMM-Newton wide-field survey in the COSMOS field. IV. X-ray spectral properties of active galactic nuclei. Astrophysical Journal, Supplement Series, 172(1), 368-382. https://doi.org/10.1086/516573