AGN with discordant optical and X-ray classification are not a physical family: Diverse origin in two AGN
arXiv:1704.01595 · doi:10.1093/mnras/stx862
Abstract
Approximately 3-17 percent of Active Galactic Nuclei (AGN) 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 AGN 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/N and both the Super Massive Black Hole (SMBH) 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.
arXiv comment13 pages, 5 figures, 7 tables, accepted for publication in MNRAS
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