{
  "id": "1010.2452",
  "version": "v1",
  "published": "2010-10-12T17:31:54.000Z",
  "updated": "2010-10-12T17:31:54.000Z",
  "title": "An Initial Mass Function for Individual Stars in Galactic Disks: I. Constraining the Shape of the IMF",
  "authors": [
    "Antonio Parravano",
    "Christopher F. McKee",
    "David J. Hollenbach"
  ],
  "comment": "46 pages, 8 figures, submitted to ApJ",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We derive a semi-empirical galactic initial mass function (IMF) from observational constraints. We assume that the star formation rate in a galaxy can be expressed as the product of the IMF, $\\psi (m)$, which is a smooth function of mass $m$ (in units of \\msun), and a time- and space-dependent total rate of star formation per unit area of galactic disk. The mass dependence of the proposed IMF is determined by five parameters: the low-mass slope $\\gamma$, the high-mass slope $-\\Gamma$, the characteristic mass $m_{ch}$ (which is close to the mass $m_{\\rm peak}$ at which the IMF turns over), and the lower and upper limits on the mass, $m_l$ (taken to be 0.004) and $m_u$ (taken to be 120). The star formation rate in terms of number of stars per unit area of galactic disk per unit logarithmic mass interval, is proportional to $m^{-\\Gamma} \\left\\{1-\\exp\\left[{-(m/m_{ch})^{\\gamma +\\Gamma}}\\right]\\right\\}$, where $\\cal N_*$ is the number of stars, $m_l<m<m_u$ is the range of stellar masses. The values of $\\gamma$ and $\\emch$ are derived from two integral constraints: i) the ratio of the number density of stars in the range $m=0.1-0.6$ to that in the range $m=0.6-0.8$ as inferred from the mass distribution of field stars in the local neighborhood, and ii) the ratio of the number of stars in the range $m=0.08 - 1$ to the number of brown dwarfs in the range $m=0.03-0.08$ in young clusters. The IMF satisfying the above constraints is characterized by the parameters $\\gamma=0.51$ and $\\emch=0.35$ (which corresponds to $m_{\\rm peak}=0.27$). This IMF agrees quite well with the Chabrier (2005) IMF for the entire mass range over which we have compared with data, but predicts significantly more stars with masses $< 0.03\\, M_\\odot$; we also compare with other IMFs in current use.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2010-10-12T17:31:54.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galactic disk",
      "individual stars",
      "star formation rate",
      "unit area",
      "semi-empirical galactic initial mass function"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/726/1/27",
      "journal": "The Astrophysical Journal",
      "year": 2011,
      "month": "Jan",
      "volume": 726,
      "number": 1,
      "pages": 27
    },
    "note": {
      "typesetting": "TeX",
      "pages": 46,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 872419,
      "adsabs": "2011ApJ...726...27P"
    }
  }
}