AGNs with discordant optical and X-ray classification are not a physical family: diverse origin in two AGNs

Ordovás-Pascual, I.I.Ordovás-PascualMateos, S.S.MateosCarrera, F. J.F. J.CarreraWiersema, K.K.WiersemaBarcons, X.X.BarconsBRAITO, ValentinaValentinaBRAITOCACCIANIGA, AlessandroAlessandroCACCIANIGADel Moro, A.A.Del MoroDELLA CECA, RobertoRobertoDELLA CECASEVERGNINI, PaolaPaolaSEVERGNINI2020-07-282020-07-2820170035-8711http://hdl.handle.net/20.500.12386/26674Approximately 3-17 per cent of active galactic nuclei (AGNs) without detected rest-frame UV/optical broad emission lines (type-2 AGN) do not show absorption in X-rays. The physical origin behind the apparently discordant optical/X-ray properties is not fully understood. Our study aims at providing insight into this issue by conducting a detailed analysis of the nuclear dust extinction and X-ray absorption properties of two AGNs with low X-ray absorption and with high optical extinction, for which a rich set of high-quality spectroscopic data is available from XMM-Newton archive data in X-rays and XSHOOTER proprietary data at UV-to-NIR wavelengths. In order to unveil the apparent mismatch, we have determined the A<SUB>V</SUB>/N<SUB>H</SUB> and both the supermassive black hole and the host galaxy masses. We find that the mismatch is caused in one case by an abnormally high dust-to-gas ratio that makes the UV/optical emission to appear more obscured than in the X-rays. For the other object, we find that the dust-to-gas ratio is similar to the Galactic one but the AGN is hosted by a very massive galaxy so that the broad emission lines and the nuclear continuum are swamped by the star light and difficult to detect.STAMPAenAGNs with discordant optical and X-ray classification are not a physical family: diverse origin in two AGNsArticle10.1093/mnras/stx8622-s2.0-85053732148000402825000048https://arxiv.org/pdf/1704.01595.pdfhttps://academic.oup.com/mnras/article/469/1/693/31922112017MNRAS.469..693OFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems