{
  "id": "1902.09654",
  "version": "v1",
  "published": "2019-02-25T23:08:56.000Z",
  "updated": "2019-02-25T23:08:56.000Z",
  "title": "Interpreting the relation between the gamma-ray and infrared luminosities of star-forming galaxies",
  "authors": [
    "Yi Zhang",
    "Fang-Kun Peng",
    "Xiang-Yu Wang"
  ],
  "comment": "9 pages, 4 figures, Accepted by ApJ",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "It has been found that there is a quasi-linear scaling relationship between the gamma-ray luminosity in GeV energies and the total infrared luminosity of star-forming galaxies, i.e. $L_{\\gamma}\\propto L_{\\rm IR}^{\\alpha}$ with $\\alpha\\simeq 1$. However, the origin of this linear slope is not well understood. Although extreme starburst galaxies can be regarded as calorimeters for hadronic cosmic ray interaction and thus a quasi-linear scaling may hold, it may not be the case for low star-formation-rate (SFR) galaxies, as the majority of cosmic rays in these galaxies are expected to escape. We calculate the gamma-ray production efficiency in star-forming galaxies by considering realistic galaxy properties, such as the gas density and galactic wind velocity in star-forming galaxies. We find that the slope for the relation between gamma-ray luminosity and the infrared luminosity gets steeper for low infrared luminosity galaxies, i.e. $\\alpha\\rightarrow 1.6$, due to increasingly lower efficiency for the production of gamma-ray emission. We further find that the measured data of the gamma-ray luminosity is compatible with such a steepening. The steepening in the slope suggests that cosmic-ray escape is very important in low-SFR galaxies.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-02-25T23:08:56.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "star-forming galaxies",
      "gamma-ray luminosity",
      "hadronic cosmic ray interaction",
      "galactic wind velocity",
      "low infrared luminosity galaxies"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}