Mon. Not. R. Astron. Soc., 426, 1750-1766 (2012/November-1)
The INTEGRAL/IBIS AGN catalogue - I. X-ray absorption properties versus optical classification.
MALIZIA A., BASSANI L., BAZZANO A., BIRD A.J., MASETTI N., PANESSA F., STEPHEN J.B. and UBERTINI P.
Abstract (from CDS):
In this work we present the most comprehensive INTEGRAL active galactic nucleus (AGN) sample. It lists 272 AGN for which we have secure optical identifications, precise optical spectroscopy and measured redshift values plus X-ray spectral information, i.e. 2–10 and 20–100keV fluxes plus column density. Here we mainly use this sample to study the absorption properties of active galaxies, to probe new AGN classes and to test the AGN unification scheme. We find that half (48 per cent) of the sample is absorbed, while the fraction of Compton-thick AGN is small ( ∼ 7 per cent). In line with our previous analysis, we have however shown that when the bias towards heavily absorbed objects which are lost if weak and at large distance is removed, as it is possible in the local Universe, the above fractions increase to become 80 and 17 per cent. We also find that absorption is a function of source luminosity, which implies some evolution in the obscuration properties of AGN. A few peculiar classes, so far poorly studied in the hard X-ray band, have been detected and studied for the first time such as 5 X-ray bright optically normal galaxies, 5 type 2 QSOs and 11 low-ionization nuclear emission regions. In terms of optical classification, our sample contains 57 per cent of type 1 and 43 per cent of type 2 AGN; this subdivision is similar to that found in X-rays if unabsorbed versus absorbed objects are considered, suggesting that the match between optical and X-ray classifications is overall good. Only a small percentage of sources (12 per cent) does not fulfil the expectation of the unified theory as we find 22 type 1 AGN which are absorbed and 10 type 2 AGN which are unabsorbed. Studying in depth these outliers we found that most of the absorbed type 1 AGN have X-ray spectra characterized by either complex or warm/ionized absorption more likely due to ionized gas located in an accretion disc wind or in the biconical structure associated with the central nucleus, therefore unrelated to the toroidal structure. Among 10 type 2 AGN which resulted to be unabsorbed, at most 3–4 per cent are still eligible to be classified as `true' type 2 AGN. The Gaia spectrophotometric standard stars survey – I. Preliminary results
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
catalogues - surveys
VizieR on-line data:
<Available at CDS (J/MNRAS/426/1750): tablea1.dat refs.dat>
Table 3: IGR J21247+5059 is a misprint for IGR J21247+5058. Table A1: SWIFT J0505.8-2348 is a misprint for SWIFT J0505.7-2348.
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