{
  "id": "1606.05309",
  "version": "v1",
  "published": "2016-06-16T18:35:11.000Z",
  "updated": "2016-06-16T18:35:11.000Z",
  "title": "Absorption Line Spectroscopy of Gravitationally-Lensed Galaxies: Further Evidence for an Increased Escape Fraction of Ionizing Photons at High Redshift",
  "authors": [
    "Nicha Leethochawalit",
    "Tucker A. Jones",
    "Richard S. Ellis",
    "Daniel P. Stark",
    "Adi Zitrin"
  ],
  "comment": "13 pages, 9 figures",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "The fraction of ionizing photons that escape from high redshift star forming galaxies remains a key obstacle in evaluating whether galaxies were the primary agents of cosmic reionization. In our earlier work, we proposed using the covering fraction of low ionization gas, measured via deep absorption line spectroscopy, as a proxy. We present a significant update using this method, sampling seven gravitationally-lensed sources in the redshift range 4<z<5. We show the absorbing gas in our sources is spatially inhomogenous with a median covering fraction of 66%. Correcting for reddening according to a dust-in-cloud model, we estimate this implies an absolute escape fraction of ~19\\pm6%. Recognizing this is higher than independent estimates based on recombination rate studies of the IGM from QSO absorption lines, we quantify possible biases and uncertainties. Collectively we find the average escape fraction could be reduced to no less than 11%, excluding the effect of spatial variations. For one of our lensed sources, we have sufficient S/N to demonstrate the presence of such spatial variations as well as scatter in its dependence on the Lya equivalent width consistent with recent simulations. If this source is typical, our lower limit to the escape fraction could be reduced by a further factor ~2. Across our sample, we find a modest anti-correlation between the inferred escape fraction and the local star formation rate consistent with a time delay between a burst and leaking LyC photons. Our analysis demonstrates considerable variations in the proportion of ionizing photons that can escape consistent with being governed by the small scale behavior of star-forming regions which fluctuate in their activities over short timescales. This supports the suggestion that the escape fraction may increase toward the reionization era when star formation becomes more energetic and burst-like.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-06-16T18:35:11.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "absorption line spectroscopy",
      "ionizing photons",
      "increased escape fraction",
      "high redshift",
      "star formation rate consistent"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 13,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}