The Compton-thick AGN in the CDF-N
  We present X-ray spectral analysis of the brightest sources (f_{2-10
keV}>10^{-15}$ cgs) in the Chandra Deep Field North. Our sample consists of 222
sources; for the vast majority (171) either a spectroscopic or a photometric
redshift is available. Our goal is to discover the Compton-thick AGN in a
direct way i.e. through their X-ray spectra. Compton-thick AGN give away their
presence in X-rays either directly through the absorption turnover redshifted
in the Chandra passband, or through a flat, reflection-dominated, spectrum. The
above selection criteria yield 10 Compton-thick AGN candidates of which the
nine are reflection dominated. The IR or sub-mm data where available,
corroborate the presence of a heavily obscured nucleus in most cases. All the
five candidate Compton-thick sources with available 24 micron data present very
high values of the f_{24}/f_R flux ratio suggesting that they are dust obscured
galaxies. The low f_x/f_{IR} ratio also suggest the presence of obscured nuclei
in many cases. Four of the candidate Compton-thick sources are associated with
sub-mm galaxies at high redshifts z$\sim2$. The number count vs. flux
distribution of the candidate Compton-thick AGN as well as their distribution
with redshift agree reasonably well with the predictions of the X-ray
background synthesis models of Gilli et al.
