{
  "id": "1306.5575",
  "version": "v1",
  "published": "2013-06-24T11:04:38.000Z",
  "updated": "2013-06-24T11:04:38.000Z",
  "title": "Condition for the formation of micron-sized dust grains in dense molecular cloud cores",
  "authors": [
    "Hiroyuki Hirashita",
    "Zhi-Yun Li"
  ],
  "comment": "5 pages, 2 figures, Accepted for publication in MNRAS Letters",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We investigate the condition for the formation of micron-sized grains in dense cores of molecular clouds. This is motivated by the detection of the mid-infrared emission from deep inside a number of dense cores, the so-called `coreshine,' which is thought to come from scattering by micron-sized grains. Based on numerical calculations of coagulation starting from the typical grain size distribution in the diffuse interstellar medium, we obtain a conservative lower limit to the time $t$ to form micron-sized grains: $t/t_\\mathrm{ff}>3 (5/S) (n_\\mathrm{H}/10^5 \\mathrm{cm}^{-3})^{-1/4}$ (where $t_\\mathrm{ff}$ is the free-fall time at hydrogen number density $n_\\mathrm{H}$ in the core, and $S$ the enhancement factor to the grain-grain collision cross-section to account for non-compact aggregates). At the typical core density $n_\\mathrm{H}=10^5 \\mathrm{cm}^{-3}$, it takes at least a few free-fall times to form the micron-sized grains responsible for coreshine. The implication is that those dense cores observed in coreshine are relatively long-lived entities in molecular clouds, rather than dynamically transient objects that last for one free-fall time or less.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2013-06-24T11:04:38.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "dense molecular cloud cores",
      "micron-sized dust grains",
      "micron-sized grains",
      "dense cores",
      "free-fall time"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1093/mnrasl/slt081",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2013,
      "month": "Jul",
      "volume": 434,
      "number": 1
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1239603,
      "adsabs": "2013MNRAS.434L..70H"
    }
  }
}