Multiwavelength studies of X-ray selected extragalactic sample
  The joint catalogue of Active Galactic Nuclei selected from optical
identifications of X-ray sources was created as a combination of two samples:
Hamburg-ROSAT Catalogue (HRC) and Byurakan-Hamburg-ROSAT Catalogue (BHRC). Both
are based on optical identifications of X-ray sources from ROSAT catalogues
using low-dispersion spectra of Hamburg Quasar Survey (HQS). However, HRC and
BHRC contain a number of misidentifications and using the recent optical and
multiwavelength (MW) catalogues we have revised both samples excluding false
AGN and adding new genuine ones. Thus a new large homogeneous complete sample
of 4253 X-ray selected AGN was created. 3352 of them are listed in the
Catalogue of QSOs and Active Galaxies and 387 also are in Roma Multifrequency
Catalogue of Blazars. 901 candidate AGN are subject for further study. We
classified 173 of these objects using their SDSS DR12 spectra. Following
activity types were revealed: 61 AGN, 21 HII galaxies, 12 emission-line
galaxies without definite type, 71 absorption-line galaxies, 2 stars, and 6
were classified as "Unknown". A special emphasis is made on narrow-line
Sy1.0-Sy1.5 galaxies and QSOs, as many of them have soft X-ray, strong FeII
lines, and relatively narrow lines coming from BLR ("narrow broad lines"). As a
result, the sample of genuine AGN was enlarged to 3413 objects. We have
retrieved MW data from recent catalogues and carried out statistical
investigations for the whole AGN sample. An attempt to find connections between
fluxes in different bands for different types of sources, and identify their
characteristics thus confirming candidate AGNs have been carried out. We have
analyzed X-ray properties of these sources to find a limit between normal
galaxies and X-ray AGN.
