In this paper we discuss the optical and X-ray spectral properties of the sources detected in a single 200 ks Chandra pointing in the Groth-Westphal Strip region .
A wealth of optical photometric and spectroscopic data are available in this field providing optical identifications and redshift determinations for the X-ray population .
The optical photometry and spectroscopy used here are primarily from the DEEP2 survey with additional redshifts obtained from the literature .
These are complemented with the deeper ( r \approx 26 mag ) multi-waveband data ( ugriz ) from the Canada France Hawaii Legacy Survey to estimate photometric redshifts and to optically identify sources fainter than the DEEP2 magnitude limit ( R _ { AB } \approx 24.5 mag ) .
We focus our study on the 2-10 keV selected sample comprising 97 sources to the limit \approx 8 \times 10 ^ { -16 } erg s ^ { -1 } cm ^ { -2 } , this being the most complete in terms of optical identification rate ( 86 % ) and redshift determination fraction ( 63 % ; both spectroscopic and photometric ) .
We first construct the redshift distribution of the sample which shows a peak at z \approx 1 .
This is in broad agreement with models where less luminous AGNs evolve out to z \approx 1 with powerful QSOs peaking at higher redshift , z \approx 2 .
Evolution similar to that of broad-line QSOs applied to the entire AGN population ( both type-I and II ) does not fit the data .
We also explore the observed N _ { H } distribution of the sample and estimate a fraction of obscured AGN ( N _ { H } > 10 ^ { 22 } cm ^ { -2 } ) of 48 \pm 9 per cent .
This is found to be consistent with both a luminosity dependent intrinsic N _ { H } distribution , where less luminous systems comprise a higher fraction of type-II AGNs and models with a fixed ratio 2:1 between type-I and II AGNs .
We further compare our results with those obtained in deeper and shallower surveys .
We argue that a luminosity dependent parametrisation of the intrinsic N _ { H } distribution is required to account for the fraction of obscured AGN observed in different samples over a wide range of fluxes .