{
  "id": "1606.02719",
  "version": "v1",
  "published": "2016-06-08T20:00:02.000Z",
  "updated": "2016-06-08T20:00:02.000Z",
  "title": "Cosmic reionization after Planck II: contribution from quasars",
  "authors": [
    "Sourav Mitra",
    "T. Roy Choudhury",
    "Andrea Ferrara"
  ],
  "comment": "6 pages, 3 figures, submitted to MNRAS",
  "categories": [
    "astro-ph.CO"
  ],
  "abstract": "In the light of the recent Planck downward revision of the electron scattering optical depth, and of the discovery of a faint QSO population at $z > 4$, we reassess the actual contribution of quasar to cosmic reionization. To this aim, we extend the data-constrained semi-analytic reionization model, based on a rigorous MCMC analysis developed in our previous works, and study the implications of such high-$z$ QSOs on the reionization history. We find that, the quasars can alone reionize the Universe only for models with very high AGN emissivities at high redshift. However, these models predict a too rapid evolution of Lyman limit systems with respect to the observed one. Models with relatively lower emissivities at high-$z$, but consistent with the present datasets, still require a non-zero escape fraction of $\\sim12\\%$ from early-epoch galaxies. For such models, reionization happens over a shorter period of time; mean neutral hydrogen fraction becomes $\\sim10^{-4}$ at $z=5.8$ from $\\sim0.8$ at $z=9.0$. Future observations of faint quasars in the early universe will be necessary to put tighter constraints on the quasar-dominated reionization scenario.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-06-08T20:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cosmic reionization",
      "contribution",
      "mean neutral hydrogen fraction",
      "data-constrained semi-analytic reionization model",
      "lyman limit systems"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}