{
  "id": "1604.08777",
  "version": "v1",
  "published": "2016-04-29T11:17:36.000Z",
  "updated": "2016-04-29T11:17:36.000Z",
  "title": "Comparing [CII], HI, and CO dynamics of nearby galaxies",
  "authors": [
    "W. J. G. de Blok",
    "F. Walter",
    "J. -D. T Smith",
    "R. Herrera-Camus",
    "A. D. Bolatto",
    "M. A. Requena-Torres",
    "A. F. Crocker",
    "K. V. Croxall",
    "R. C. Kennicutt",
    "J. Koda",
    "L. Armus",
    "M. Boquien",
    "D. Dale",
    "K. Kreckel",
    "S. Meidt"
  ],
  "comment": "Accepted for publication in the Astronomical Journal",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "The HI and CO components of the interstellar medium (ISM) are usually used to derive the dynamical mass M_dyn of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those cases, the 158 $\\mu$m line of atomic carbon [CII] may be the only way to derive M_dyn. As the distribution and kinematics of the ISM tracer affects the determination of M_dyn, it is important to quantify the relative distributions of HI, CO and [CII]. HI and CO are well-characterised observationally, however, for [CII] only very few measurements exist. Here we compare observations of CO, HI, and [CII] emission of a sample of nearby galaxies, drawn from the HERACLES, THINGS and KINGFISH surveys. We find that within R_25, the average [CII] exponential radial profile is slightly shallower than that of the CO, but much steeper than the HI distribution. This is also reflected in the integrated spectrum (\"global profile\"), where the [CII] spectrum looks more like that of the CO than that of the HI. For one galaxy, a spectrally resolved comparison of integrated spectra was possible; other comparisons were limited by the intrinsic line-widths of the galaxies and the coarse velocity resolution of the [CII] data. Using high-spectral-resolution SOFIA [CII] data of a number of star forming regions in two nearby galaxies, we find that their [CII] linewidths agree better with those of the CO than the HI. As the radial extent of a given ISM tracer is a key input in deriving M_dyn from spatially unresolved data, we conclude that the relevant length-scale to use in determining M_dyn based on [CII] data, is that of the well-characterised CO distribution. This length scale is similar to that of the optical disk.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-04-29T11:17:36.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nearby galaxies",
      "linewidths agree better",
      "ism tracer affects",
      "integrated spectrum",
      "coarse velocity resolution"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}