{
  "id": "1009.6005",
  "version": "v1",
  "published": "2010-09-29T21:09:50.000Z",
  "updated": "2010-09-29T21:09:50.000Z",
  "title": "The Effects of X-Ray and UV Background Radiation on the Low-Mass Slope of the Galaxy Mass Function",
  "authors": [
    "D. C. Hambrick",
    "J. P. Ostriker",
    "P. H. Johansson",
    "T. Naab"
  ],
  "comment": "9 pages, 4 figures in mn2e style; submitted to MNRAS",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "Even though the dark-matter power spectrum in the absence of biasing predicts a number density of halos n(M) ~ M^-2 (i.e. a Schechter alpha value of -2) at the low-mass end (M < 10^10 M_solar), hydrodynamic simulations have typically produced values for stellar systems in good agreement with the observed value alpha ~ -1. We explain this with a simple physical argument and show that an efficient external gas-heating mechanism (such as the UV background included in all hydro codes) will produce a critical halo mass below which halos cannot retain their gas and form stars. We test this conclusion with GADGET-2-based simulations using various UV backgrounds, and for the first time we also investigate the effect of an X-ray background. We show that at the present epoch alpha is depends primarily on the mean gas temperature at the star-formation epoch for low-mass systems (z <~ 3): with no background we find alpha ~ -1.5, with UV only alpha ~ -1.0, and with UV and X-rays alpha ~ -0.75. We find the critical final halo mass for star formation to be ~4x10^8 M_solar with a UV background and ~7x10^8 M_solar with UV and X-rays.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2010-09-29T21:09:50.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galaxy mass function",
      "uv background radiation",
      "low-mass slope",
      "halo mass",
      "efficient external gas-heating mechanism"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1111/j.1365-2966.2011.18312.x",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2011,
      "month": "Jun",
      "volume": 413,
      "number": 4,
      "pages": 2421
    },
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 871314,
      "adsabs": "2011MNRAS.413.2421H"
    }
  }
}