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|Title:||A Deep X-Ray View of the Bare AGN Ark 120. I. Revealing the Soft X-Ray Line Emission||Authors:||Reeves, J. N.
Turner, T. J.
|Issue Date:||2016||Journal:||THE ASTROPHYSICAL JOURNAL||Number:||828||Issue:||2||First Page:||98||Abstract:||The 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.||URI:||http://hdl.handle.net/20.500.12386/25167||URL:||https://iopscience.iop.org/article/10.3847/0004-637X/828/2/98
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Sep 29, 2020
checked on Sep 29, 2020
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