{
  "id": "0708.4362",
  "version": "v1",
  "published": "2007-08-31T17:52:43.000Z",
  "updated": "2007-08-31T17:52:43.000Z",
  "title": "The Metallicity of Intergalactic Gas in Cosmic Voids",
  "authors": [
    "John T. Stocke",
    "Charles W. Danforth",
    "J. Michael Shull",
    "Steven V. Penton",
    "Mark L. Giroux"
  ],
  "comment": "Accepted for ApJ, 8 pages including Fig 1a,b",
  "doi": "10.1086/522920",
  "categories": [
    "astro-ph"
  ],
  "abstract": "We have used the Hubble/STIS and FUSE archives of ultraviolet spectra of bright AGN to identify intergalactic Lya absorbers in nearby (z < 0.1) voids. From a parent sample of 651 Lya absorbers, we identified 61 void absorbers located more than 1.4/h_70 Mpc from the nearest L* or brighter galaxy. Searching for metal absorption in high-quality (S/N > 10) spectra at the location of three diagnostic metal lines (O VI 1032, C IV 1548, Si III 1206), we detected no metal lines in any individual absorber, or in any group of absorbers using pixel co-addition techniques. The best limits on metal-line absorption in voids were set using four strong Lya absorbers with N(H I) > 10^{14} cm^-2, with 3-sigma equivalent-width limits ranging from 8 mA (O VI), 7-15 mA (C IV), and 4-10 mA (Si III). Photoionization modeling yields metallicity limits Z < 10^{-1.8+/-0.4} Z_sun, from non-detections of C IV and O VI, some 6 times lower than those seen in Lya and OVI absorbers at z < 0.1. Although the void Lya absorbers could be pristine material, considerably deeper spectra are required to rule out a universal metallicity floor produced by bursts of early star formation, with no subsequent star formation in the voids. The most consistent conclusion derived from these low-z results, and similar searches at z = 3-5, is that galaxy filaments have increased their mean IGM metallicity by factors of 30-100 since z = 3.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2007-08-31T17:52:43.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "intergalactic gas",
      "cosmic voids",
      "photoionization modeling yields metallicity limits",
      "star formation",
      "metal lines"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "journal": "The Astrophysical Journal",
      "year": 2007,
      "month": "Dec",
      "volume": 671,
      "number": 1,
      "pages": 146
    },
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 759547,
      "adsabs": "2007ApJ...671..146S"
    }
  }
}