{
  "id": "2410.10988",
  "version": "v1",
  "published": "2024-10-14T18:15:54.000Z",
  "updated": "2024-10-14T18:15:54.000Z",
  "title": "The evolution of [OIII]$+\\rm{H}β$ equivalent width from $\\mathbf{z\\simeq3-8}$: implications for the production and escape of ionizing photons during reionization",
  "authors": [
    "R. Begley",
    "R. J. McLure",
    "F. Cullen",
    "D. J. McLeod",
    "J. S. Dunlop",
    "A. C. Carnall",
    "T. M. Stanton",
    "A. E. Shapley",
    "R. Cochrane",
    "C. T. Donnan",
    "R. S. Ellis",
    "A. Fontana",
    "N. A. Grogin",
    "A. M. Koekemoer"
  ],
  "comment": "18 pages, 9 figures + 1 appendix. Submitted to MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Accurately quantifying the ionizing photon production efficiency ($\\xi_\\rm{ion}$) of $z>6$ star-forming galaxies (SFGs) is necessary to understand their contribution to reionization. We investigate the ionizing properties of N=289 SFGs selected at $z=6.9-7.6$ from the JWST Cycle-1 imaging programmes; PRIMER and JADES. We use BAGPIPES to consistently infer the equivalent widths of their [OIII]+$\\rm{H\\beta}$ emission lines ($W_\\lambda$) and their physical properties. To supplement our high-redshift galaxies, we measure $W_\\lambda$ photometrically for a sample of N=253 $z=3.2-3.6$ SFGs selected from the VANDELS spectroscopic survey. Comparing these samples, we find a strong apparent redshift evolution in their median $W_\\lambda$, increasing from $W_\\lambda =310\\pm25\\,\\r{A}$ in VANDELS to $W_\\lambda =630\\pm30\\,\\r{A}$ in our JWST-based sample. In the JWST sample at $z>7$, we find that $W_\\lambda$ correlates with both stellar mass and UV luminosity, with high-mass, $M_{ UV}-$faint galaxies producing systematically weaker emission lines. Moreover, we discover a departure from the standard log-normal shape of the $W_\\lambda$ distribution, characterised by a more pronounced tail at lower $W_\\lambda$, consistent with increasingly bursty star formation. Using $W_\\lambda$ as a proxy for $\\xi_\\rm{ion}$, and UV spectral slope as a proxy for LyC escape fraction ($f_\\rm{esc}$), we find a minority of galaxies with high $\\xi_\\rm{ion}$ and $f_\\rm{esc}$ (e.g., $\\rm{log(\\xi_{ion}/erg^{-1}Hz})\\sim25.6$ and $f_\\rm{esc}\\sim0.15$). However, we find that the LyC photon budget at $z>7$ is dominated by galaxies with more moderate output, close to the sample median of $\\rm{log(\\xi_{ion}/erg^{-1}Hz})\\sim25.3$ and $f_\\rm{esc}\\sim0.05$. This is consistent with estimates for the number of LyC photons required to power reionization at $z>7$, with no evidence for over or under-production.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-10-14T18:15:54.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "equivalent width",
      "ionizing photon",
      "systematically weaker emission lines",
      "producing systematically weaker emission",
      "reionization"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 18,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}