{
  "id": "1908.07536",
  "version": "v1",
  "published": "2019-08-20T18:00:02.000Z",
  "updated": "2019-08-20T18:00:02.000Z",
  "title": "A physical model for [CII] line emission from galaxies",
  "authors": [
    "A. Ferrara",
    "L. Vallini",
    "A. Pallottini",
    "S. Gallerani",
    "S. Carniani",
    "M. Kohandel",
    "D. Decataldo",
    "C. Behrens"
  ],
  "comment": "Accepted for publication in MNRAS. 12 pages, 6 Figures. Comments welcome",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "A tight relation between the [CII]158$\\mu$m line luminosity and star formation rate is measured in local galaxies. At high redshift ($z>5$), though, a much larger scatter is observed, with a considerable (15-20\\%) fraction of the outliers being [CII]-deficient. Moreover, the [CII] surface brightness ($\\Sigma_{\\rm CII}$) of these sources is systematically lower than expected from the local relation. To clarify the origin of such [CII]-deficiency we have developed an analytical model that fits local [CII] data, and has been validated against radiative transfer simulations performed with CLOUDY. The model predicts an overall increase of $\\Sigma_{\\rm CII}$ with the surface star formation rate ($\\Sigma_*$). However, for $\\Sigma_* > 1 M_\\odot~{\\rm yr}^{-1}~{\\rm kpc}^{-2}$, $\\Sigma_{\\rm CII}$ saturates. We conclude that underluminous [CII] systems can result from a combination of three factors: (a) large upward deviations from the Kennicutt-Schmidt relation ($\\kappa_s \\gg 1$), parameterized by the \"burstiness\" parameter $\\kappa_s$; (b) low metallicity; (c) low gas density, at least for the most extreme sources (e.g. CR7). Observations of [CII] emission alone cannot break the degeneracy among the above three parameters; this requires additional information coming from other emission lines (e.g. [OIII]88$\\mu$m, CIII]1909A, CO lines). Simple formulae are given to interpret available data for low and high-$z$ galaxies.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-08-20T18:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "line emission",
      "physical model",
      "surface star formation rate",
      "low gas density",
      "model predicts"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}