{
  "id": "2311.13683",
  "version": "v1",
  "published": "2023-11-22T20:34:17.000Z",
  "updated": "2023-11-22T20:34:17.000Z",
  "title": "JWST spectroscopy of $z\\sim 5-8$ UV-selected galaxies: New constraints on the evolution of the Ly$α$ escape fraction in the reionization era",
  "authors": [
    "Zuyi Chen",
    "Daniel P. Stark",
    "Charlotte Mason",
    "Michael W. Topping",
    "Lily Whitler",
    "Mengtao Tang",
    "Ryan Endsley",
    "Stéphane Charlot"
  ],
  "comment": "main text 19 pages, 12 figures",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We describe {\\it JWST}/NIRSpec prism measurements of Ly$\\alpha$ emission in $z\\gtrsim 5$ galaxies. We identify Ly$\\alpha$ detections in 10 out of 69 galaxies with robust rest-optical emission line redshift measurements at $5\\leq z<7$ in the CEERS and DDT-2750 observations of the EGS field. Galaxies at $z\\simeq 6$ with faint continuum (F150W $=$ 27--29 mag) are found with extremely large Ly$\\alpha$ equivalent widths (ranging up to 286 A). Likely Ly$\\alpha$ detections are also seen in two new $z>7$ galaxies ($z=$ 7.49 and 7.17) from the second epoch of CEERS observations, both of which show large Ly$\\alpha$ equivalent widths that likely indicate significant transmission through the IGM. We measure high Ly$\\alpha$ escape fractions in the 12 Ly$\\alpha$ emitters in our sample (median 0.28), two of which show $f_{\\rm esc}^{ {\\rm Ly}\\alpha}$ near unity ($>0.80$). We find that $50_{-11}^{+11}$% of $z\\simeq 6$ galaxies with [OIII]+H$\\beta$ EW $>$ 1000 A have $f_{\\rm esc}^{ {\\rm Ly}\\alpha}$ $>0.2$, consistent with the fractions found in lower-redshift samples with matched [OIII]+H$\\beta$ EWs. While uncertainties are still significant, we find that only $10_{-5}^{+9}$% of $z>7$ galaxies with similarly strong rest optical emission lines show such large $f_{\\rm esc}^{ {\\rm Ly}\\alpha}$, as may be expected if IGM attenuation of Ly$\\alpha$ increases towards higher redshifts. We identify photometric galaxy overdensities near the $z\\gtrsim 7$ Ly$\\alpha$ emitters, potentially providing the ionizing flux necessary to create large ionized sightlines that facilitate Ly$\\alpha$ transmission. Finally, we investigate the absence of Ly$\\alpha$ emission in a comparable (and spectroscopically confirmed) galaxy overdensity at $z=7.88$ in the Abell 2744 field, discussing new prism spectra of the field obtained with the UNCOVER program.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-11-22T20:34:17.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "escape fraction",
      "reionization era",
      "jwst spectroscopy",
      "strong rest optical emission",
      "rest optical emission lines"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 19,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}