{
  "id": "1607.01062",
  "version": "v1",
  "published": "2016-07-04T22:09:16.000Z",
  "updated": "2016-07-04T22:09:16.000Z",
  "title": "A deep X-ray view of the bare AGN Ark 120. I. Revealing the Soft X-ray Line Emission",
  "authors": [
    "James Reeves",
    "Delphine Porquet",
    "Valentina Braito",
    "Emanuele Nardini",
    "Andrew Lobban",
    "Jane Turner"
  ],
  "comment": "42 pages, 10 figures, accepted for publication in the Astrophysical Journal",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "The Seyfert 1 galaxy, Ark 120, is a prototype example of the so-called class of bare nucleus AGN, 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 which were carried out in March 2014, together with simultaneous Chandra/HETG 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 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 neighbourhood. However, the presence of several soft X-ray emission lines are revealed for the first time in the XMM-Newton RGS spectrum, associated to 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 FWHM widths of $\\sim5000$ km s$^{-1}$, whereas the H-like profiles are unresolved. From the clean measurement of the He-like triplets, we deduce that the broad lines arise from gas of density $n_{\\rm e}\\sim10^{11}$ cm$^{-3}$, while the photoionization calculations infer that the emitting gas covers at least 10 percent of $4\\pi$ steradian. Thus the broad soft X-ray profiles appear coincident with an X-ray component of the optical-UV Broad Line Region on sub-pc scales, whereas the narrow profiles originate on larger pc 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 towards this AGN.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-07-04T22:09:16.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "soft x-ray line emission",
      "bare agn ark",
      "deep x-ray view",
      "soft x-ray profiles appear",
      "x-ray profiles appear coincident"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 42,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}