{
  "id": "1607.02511",
  "version": "v1",
  "published": "2016-07-08T20:00:02.000Z",
  "updated": "2016-07-08T20:00:02.000Z",
  "title": "Far-infrared line spectra of active galaxies from the Herschel/PACS Spectrometer: the complete database",
  "authors": [
    "J. A. Fernández-Ontiveros",
    "L. Spinoglio",
    "M. Pereira-Santaella",
    "M. A. Malkan",
    "P. Andreani",
    "K. M. Dasyra"
  ],
  "comment": "Accepted for publication in the ApJS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present a coherent database of spectroscopic observations of far-IR fine-structure lines from the Herschel/PACS archive for a sample of 170 local AGN, plus a comparison sample of 20 starburst galaxies and 43 dwarf galaxies. Published Spitzer/IRS and Herschel/SPIRE line fluxes are included to extend our database to the full 10-600 $\\mu m$ spectral range. The observations are compared to a set of CLOUDY photoionisation models to estimate the above physical quantities through different diagnostic diagrams. We confirm the presence of a stratification of gas density in the emission regions of the galaxies, which increases with the ionisation potential of the emission lines. The new [OIV]25.9$\\mu m$/[OIII]88$\\mu m$ vs [NeIII]15.6$\\mu m$/[NeII]12.8$\\mu m$ diagram is proposed as the best diagnostic to separate: $i)$ AGN activity from any kind of star formation; and $ii)$ low-metallicity dwarf galaxies from starburst galaxies. Current stellar atmosphere models fail to reproduce the observed [OIV]25.9$\\mu m$/[OIII]88$\\mu m$ ratios, which are much higher when compared to the predicted values. Finally, the ([NeIII]15.6$\\mu m$ + [NeII]12.8$\\mu m$)/([SIV]10.5$\\mu m$ + [SIII]18.7$\\mu m$) ratio is proposed as a promising metallicity tracer to be used in obscured objects, where optical lines fail to accurately measure the metallicity. The diagnostic power of mid- to far-infrared spectroscopy shown here for local galaxies will be of crucial importance to study galaxy evolution during the dust-obscured phase at the peak of the star formation and black-hole accretion activity ($1 < z < 4$). This study will be addressed by future deep spectroscopic surveys with present and forthcoming facilities such as JWST, ALMA, and SPICA.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-07-08T20:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "far-infrared line spectra",
      "herschel/pacs spectrometer",
      "complete database",
      "active galaxies",
      "current stellar atmosphere models fail"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}