Reeves, J. N.J. N.ReevesPorquet, D.D.PorquetBRAITO, ValentinaValentinaBRAITONARDINI, EMANUELEEMANUELENARDINILobban, A.A.LobbanTurner, T. J.T. J.Turner2020-05-262020-05-2620160004-637Xhttp://hdl.handle.net/20.500.12386/25167The Seyfert 1 galaxy Ark 120 is a prototype example of the so-called class of bare nucleus active galactic nuclei (AGNs), whereby there is no known evidence for the presence of ionized gas along the direct line of sight. Here deep (>400 ks exposure), high-resolution X-ray spectroscopy of Ark 120 is presented from XMM-Newton observations that were carried out in 2014 March, together with simultaneous Chandra/High Energy Transmission Grating exposures. The high-resolution spectra confirmed the lack of intrinsic absorbing gas associated with Ark 120, with the only X-ray absorption present originating from the interstellar medium (ISM) of our own Galaxy, with a possible slight enhancement of the oxygen abundance required with respect to the expected ISM values in the solar neighborhood. However, the presence of several soft X-ray emission lines are revealed for the first time in the XMM-Newton RGS spectrum, associated with the AGN and arising from the He- and H-like ions of N, O, Ne, and Mg. The He-like line profiles of N, O, and Ne appear velocity broadened, with typical FWHMs of ∼5000 km s<SUP>-1</SUP>, whereas the H-like profiles are unresolved. From the clean measurement of the He-like triplets, we deduce that the broad lines arise from a gas of density n <SUB>e</SUB> ∼ 10<SUP>11</SUP> cm<SUP>-3</SUP>, while the photoionization calculations infer that the emitting gas covers at least 10% of 4π steradian. Thus the broad soft X-ray profiles appear coincident with an X-ray component of the optical-UV broad-line region on sub-parsec scales, whereas the narrow profiles originate on larger parsec scales, perhaps coincident with the AGN narrow-line region. The observations show that Ark 120 is not intrinsically bare and substantial X-ray-emitting gas exists out of our direct line of sight toward this AGN.STAMPAenArticle10.3847/0004-637X/828/2/982-s2.0-84991696876000384237800004https://iopscience.iop.org/article/10.3847/0004-637X/828/2/98https://iopscience.iop.org/article/10.3847/0004-637X/828/2/98/pdf2016ApJ...828...98RFIS/05 - ASTRONOMIA E ASTROFISICA