A deep X-ray view of the bare AGN Ark 120. I. Revealing the Soft X-ray Line Emission

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 $\sim 5000$ 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 $n_{\mathrm{e}}\sim 10^{11}$ 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.

42 pages, 10 figures, accepted for publication in the Astrophysical Journal

References in corpus (10)

• A fast and long-lived outflow from the supermassive black hole in NGC 5548
• X-ray Absorption and Reflection in Active Galactic Nuclei
• Tracing a Disk Wind in NGC 3516
• The Seyfert 1 Galaxy Mrk 335 at a very low flux state: mapping the soft X-ray photoionised gas
• NGC 1365: A low column density state unveiling a low ionization disk wind
• Modeling the Fe K Line Profiles in Type I AGN with a Compton-Thick Disk Wind
• An X-ray look at the Seyfert 1 Galaxy Mrk 590: XMM-Newton and Chandra reveal complexity in circumnuclear gas
• Physical properties of the interstellar medium using high-resolution Chandra spectra: O K-edge absorption
• Multiwavelength Campaign on Mrk 509 X. Lower limit on the distance of the absorber from HST COS and STIS spectroscopy
• Multiwavelength campaign on Mrk 509 IX. The Galactic foreground

Cited by in corpus (17)

• A deep X-ray view of the bare AGN Ark120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes
• Searching for Ultra-fast Outflows in AGN using Variability Spectra
• A deep X-ray view of the bare AGN Ark120. V. Spin determination from disc-Comptonisation efficiency method
• The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy
• A deep X-ray view of the bare AGN Ark 120. II. Evidence for Fe K emission transients
• The first broadband X-ray view of the narrow line Seyfert 1 Ton S180
• The flaring X-ray corona in the quasar PDS 456
• A deep X-ray view of the bare AGN Ark 120. III. X-ray timing analysis and multiwavelength variability
• X-ray, UV and optical time delays in the bright Seyfert galaxy Ark 120 with co-ordinated Swift and ground-based observations
• Long term X-Ray Observations of Seyfert 1 Galaxy Ark 120: On the origin of soft-excess
• Constraints on the ultra-fast outflows in the narrow-line Seyfert 1 galaxy Mrk 1044 from high-resolution time- and flux-resolved spectroscopy
• Tracking the state transitions in changing-look active galactic nuclei through their polarized-light echoes
• High Resolution X-ray Spectroscopy of the Seyfert 1, Mrk 1040. Revealing the Failed Nuclear Wind with Chandra
• Variable oxygen emission from the accretion disk of Mrk 110
• A UV to X-ray view of soft excess in type 1 AGNs: I. sample selection and spectral profile
• X-ray line coincidence photopumping in a solar flare
• A possible two-fold scenario for the disc-corona of the luminous AGN 1H 0419--577: a high-density disc or a warm corona