{
  "id": "1507.00340",
  "version": "v1",
  "published": "2015-07-01T20:00:28.000Z",
  "updated": "2015-07-01T20:00:28.000Z",
  "title": "On the [CII]-SFR relation in high redshift galaxies",
  "authors": [
    "L. Vallini",
    "S. Gallerani",
    "A. Ferrara",
    "A. Pallottini",
    "B. Yue"
  ],
  "comment": "7 pages, 5 figures",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "After two ALMA observing cycles, only a handful of [CII] $158\\,\\mu m$ emission line searches in z>6 galaxies have reported a positive detection, questioning the applicability of the local [CII]-SFR relation to high-z systems. To investigate this issue we use the Vallini et al. 2013 (V13) model, based on high-resolution, radiative transfer cosmological simulations to predict the [CII] emission from the interstellar medium of a z~7 (halo mass $M_h=1.17\\times10^{11}M_{\\odot}$) galaxy. We improve the V13 model by including (a) a physically-motivated metallicity (Z) distribution of the gas, (b) the contribution of Photo-Dissociation Regions (PDRs), (c) the effects of Cosmic Microwave Background on the [CII] line luminosity. We study the relative contribution of diffuse neutral gas to the total [CII] emission ($F _{diff}/F_{tot}$) for different SFR and Z values. We find that the [CII] emission arises predominantly from PDRs: regardless of the galaxy properties, $F _{diff}/F_{tot}\\leq 10$% since, at these early epochs, the CMB temperature approaches the spin temperature of the [CII] transition in the cold neutral medium ($T_{CMB}\\sim T_s^{CNM}\\sim 20$ K). Our model predicts a high-z [CII]-SFR relation consistent with observations of local dwarf galaxies ($0.02<Z/Z_{\\odot}<0.5$). The [CII] deficit suggested by actual data ($L_{CII}<2.0\\times 10^7 L_{\\odot}$ in BDF3299 at z~7.1) if confirmed by deeper ALMA observations, can be ascribed to negative stellar feedback disrupting molecular clouds around star formation sites. The deviation from the local [CII]-SFR would then imply a modified Kennicutt-Schmidt relation in z>6 galaxies. Alternatively/in addition, the deficit might be explained by low gas metallicities ($Z<0.1 Z_{\\odot}$).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-07-01T20:00:28.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high redshift galaxies",
      "stellar feedback disrupting molecular clouds",
      "cmb temperature approaches",
      "emission line searches",
      "star formation sites"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 7,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}