X-ray observations of dust obscured galaxies in the Chandra Deep Field
  South
  We present the properties of X-ray detected dust obscured galaxies (DOGs) in
the Chandra Deep Field South. In recent years, it has been proposed that a
significant percentage of the elusive Compton-thick (CT) active galactic nuclei
(AGN) could be hidden among DOGs. In a previous work, we presented the
properties of X-ray detected DOGs by making use of the deepest X-ray
observations available at that time, the 2Ms observations of the Chandra deep
fields. In that work, we only found a moderate percentage ($<$ 50%) of CT AGN
among the DOGs sample, but we were limited by poor photon statistics. In this
paper, we use not only a deeper 6 Ms Chandra survey of the Chandra Deep Field
South (CDF-S), but combine these data with the 3 Ms XMM-Newton survey of the
CDF-S. We also take advantage of the great coverage of the CDF-S region from
the UV to the far-IR to fit the spectral energy distributions (SEDs) of our
sources. Out of the 14 AGN composing our sample, 9 are highly absorbed (but
only 3 could be CT AGN), whereas 2 look unabsorbed, and the other 3 are only
moderately absorbed. In only one of the CT AGN, we detect a strong Fe K$\alpha$
emission line; the source is already classified as a CT AGN with Chandra data
in a previous work. For the other two CT candidates, the non-detection of the
line could be because of the low number of counts in their X-ray spectra, but
their location in the L$_{\rm 2-10\,keV}$/L$_{12\mu m}$ plot supports their CT
classification. Although a higher number of CT sources could be hidden among
the X-ray undetected DOGs, our results indicate that DOGs could be as well
composed of only a fraction of CT AGN plus a number of moderate to highly
absorbed AGN, as previously suggested. From our study of the X-ray undetected
DOGs in the CDF-S, we estimate a percentage between 13 and 44% of CT AGN among
the whole population of DOGs.
