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 language | English (US) |
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Pages (from-to) | 368-382 |
Number of pages | 15 |
Journal | Astrophysical Journal, Supplement Series |
Volume | 172 |
Issue number | 1 |
DOIs | |
State | Published - 2007 |
Externally published | Yes |
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