SIMBAD references

We present the results of optical spectroscopic identifications of a bright subsample of 2-10 keV hard X-ray-selected sources from the ASCA Medium Sensitivity Survey in the northern sky (AMSSn). The flux limit of the subsample is 3x10^–13 erg/s/cm² in the 2-10 keV band. All but one of the 87 hard X-ray-selected sources are optically identified, with AGNs (including broad-line AGNs, narrow-line AGNs, and three BL Lac objects), seven clusters of galaxies, and one galactic star. It is the largest complete sample of hard X-ray-selected AGNs at the bright flux limit. Amounts of absorption to their nuclei are estimated to be hydrogen column densities (N_H) of up to ∼3x10²³ cm^–2 from their X-ray spectra. Optical properties of X-ray absorbed AGNs with N_H>1x10²² cm^–2 indicate the effects of dust absorption: at redshifts z<0.6, AGNs without broad Hβ emission lines have significantly larger N_H-values than AGNs with broad Hβ emission lines. At z>0.6, the X-ray absorbed AGNs have a large hard X-ray to optical flux ratio (logf_2–10keV/f_R>+1). However, three X-ray absorbed z>0.6 AGNs show strong broad lines. In combination with hard X-ray-selected AGN samples from the ASCA Large Sky Survey, the ASCA Deep Survey in the Lockman Hole, and Chandra Deep Field North, the luminosity distributions of absorbed (N_H>1x10²² cm^–2) and less-absorbed (N_H<1x10²² cm^–2) AGNs are compared.