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Journal Articles Astronomy and Astrophysics - A&A Year : 2013

The XMM deep survey in the CDF-S

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I. Georgantopoulos
  • Function : Author
A. Comastri
  • Function : Author
C. Vignali
P. Ranalli
  • Function : Author
E. Rovilos
  • Function : Author
K. Iwasawa
  • Function : Author
R. Gilli
  • Function : Author
N. Cappelluti
  • Function : Author
F. Carrera
  • Function : Author
J. Fritz
  • Function : Author
M. Brusa
  • Function : Author
R. J. Mullaney
  • Function : Author
N. Castello-Mor
  • Function : Author
X. Barcons
  • Function : Author
P. Tozzi
  • Function : Author
I. Balestra
  • Function : Author
S. Falocco
  • Function : Author


The Chandra Deep Field is the region of the sky with the highest concentration of X-ray data available: 4 Ms of Chandra and 3 Ms of XMM-Newton data, allowing excellent quality spectra to be extracted even for faint sources. We took advantage of this to compile a sample of heavily obscured active galactic nuclei (AGN) using X-ray spectroscopy. We selected our sample among the 176 brightest XMM-Newton sources, searching for either flat X-ray spectra (Γ < 1.4 at the 90% confidence level) suggestive of a reflection dominated continuum or an absorption turn-over suggestive of a column density higher than ≈ 1024 cm-2. We found a sample of nine heavily-obscured sources satisfying the above criteria. Four of these show statistically significant FeKα lines with large equivalent widths (three out of four have equivalent widths consistent with 1 keV) suggesting that these are the most certain Compton-thick AGN candidates. Two of these sources are transmission dominated while the other two are most probably reflection dominated Compton-thick AGN. Although this sample of four sources is by no means statistically complete, it represents the best example of Compton-thick sources found at moderate-to-high redshift with three sources at z = 1.2–1.5 and one source at z = 3.7. Using Spitzer and Herschel observations, we estimate with good accuracy the X-ray to mid-IR (12  μm) luminosity ratio of our sources. These are well below the average AGN relation, independently suggesting that these four sources are heavily obscured.
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cea-01135402 , version 1 (25-03-2015)



I. Georgantopoulos, A. Comastri, C. Vignali, P. Ranalli, E. Rovilos, et al.. The XMM deep survey in the CDF-S. Astronomy and Astrophysics - A&A, 2013, 555, pp.A43. ⟨10.1051/0004-6361/201220828⟩. ⟨cea-01135402⟩
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