{
  "id": "2006.10065",
  "version": "v1",
  "published": "2020-06-17T18:00:03.000Z",
  "updated": "2020-06-17T18:00:03.000Z",
  "title": "The contribution of globular clusters to cosmic reionization",
  "authors": [
    "Xiangcheng Ma",
    "Eliot Quataert",
    "Andrew Wetzel",
    "Claude-André Faucher-Giguère",
    "Michael Boylan-Kolchin"
  ],
  "comment": "10 pages, 7 figures, comments welcome, key results in Table 3 and Figure 3",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We study the escape fraction of ionizing photons (f_esc) in two cosmological zoom-in simulations of galaxies in the reionization era with halo mass M_halo~10^10 and 10^11 M_sun (stellar mass M*~10^7 and 10^9 M_sun) at z=5 from the Feedback in Realistic Environments project. These simulations explicitly resolve the formation of proto-globular clusters (GCs) self-consistently, where 17-39% of stars form in bound clusters during starbursts. Using post-processing Monte Carlo radiative transfer calculations of ionizing radiation, we compute f_esc from cluster stars and non-cluster stars formed during a starburst over ~100 Myr in each galaxy. We find that the averaged f_esc over the lifetime of a star particle follows a similar distribution for cluster stars and non-cluster stars. Clusters tend to have low f_esc in the first few Myrs, presumably because they form preferentially in more extreme environments with high optical depths; the f_esc increases later as feedback starts to disrupt the natal cloud. On the other hand, non-cluster stars formed between cluster complexes or in the compressed shell at the front of a superbubble can also have high f_esc. We find that cluster stars on average have comparable f_esc to non-cluster stars. This result is robust across several star formation models in our simulations. Our results suggest that the fraction of ionizing photons from proto-GCs to cosmic reionization is comparable to the cluster formation efficiency in high-redshift galaxies and hence proto-GCs likely contribute an appreciable fraction of photons but are not the dominant sources for reionization.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-06-17T18:00:03.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cosmic reionization",
      "non-cluster stars",
      "globular clusters",
      "monte carlo radiative transfer calculations",
      "contribution"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}