CaltechAUTHORS
Published April 2023 | Version Published
Journal Article Open

Closing in on the sources of cosmic reionization: First results from the GLASS-JWST program

Creators

  • 1. ROR icon Astronomical Observatory of Rome
  • 2. ROR icon University of Rome Tor Vergata
  • 3. ROR icon University of California, Los Angeles
  • 4. ROR icon Kavli Institute for the Physics and Mathematics of the Universe
  • 5. ROR icon University of Milan
  • 6. ROR icon Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano
  • 7. ROR icon University of Ferrara
  • 8. ROR icon Osservatorio Astronomico di Padova
  • 9. ROR icon University of Melbourne
  • 10. ROR icon Centre of Excellence for All-Sky Astrophysics
  • 11. ROR icon Swinburne University of Technology
  • 12. ROR icon Space Telescope Science Institute
  • 13. ROR icon Johns Hopkins University
  • 14. ROR icon University of Copenhagen
  • 15. ROR icon Infrared Processing and Analysis Center
  • 16. ROR icon University of Minnesota
  • 17. ROR icon University of Chinese Academy of Sciences
  • 18. ROR icon National Astronomical Observatories
  • 19. ROR icon Beijing Normal University
  • 20. ROR icon University of Ljubljana
  • 21. ROR icon University of California, Davis
  • 22. ROR icon Arizona State University

Abstract

The escape fraction of Lyman-continuum (LyC) photons (f_(esc)) is a key parameter for determining the sources of cosmic reionization at z ≥ 6. At these redshifts, owing to the opacity of the intergalactic medium, the LyC emission cannot be measured directly. However, LyC leakers during the epoch of reionization could be identified using indirect indicators that have been extensively tested at low and intermediate redshifts. These include a high [O III]/[O II] flux ratio, high star-formation surface density, and compact sizes. In this work, we present observations of 29 4.5 ≤ z ≤ 8 gravitationally lensed galaxies in the Abell 2744 cluster field. From a combined analysis of JWST-NIRSpec and NIRCam data, we accurately derived their physical and spectroscopic properties: our galaxies have low masses (log(M⋆)∼8.5), blue UV spectral slopes (β ∼ −2.1), compact sizes (r_e ∼ 0.3 − 0.5 kpc), and high [O III]/[O II] flux ratios. We confirm that these properties are similar to those characterizing low-redshift LyC leakers. Indirectly inferring the fraction of escaping ionizing photons, we find that more than 80% of our galaxies have predicted f_(esc) values larger than 0.05, indicating that they would be considered leakers. The average predicted f_(esc) value of our sample is 0.12, suggesting that similar galaxies at z ≥ 6 have provided a substantial contribution to cosmic reionization.

Additional Information

© The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication. Support for program JWST-ERS-1324 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs GLASS-JWST #1324, JWST DDT #2756 and GO UNCOVER #2561. S.M. thanks the Department of Physics and Astronomy at the University of California, Los Angeles, for a productive and satisfying visit in which the majority of the work presented in this paper was done. We acknowledge support from the INAF Large Grant 2022 "Extragalactic Surveys with JWST" (PI: Pentericci). This research is supported in part by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. L.Y. acknowledges support by JSPS KAKENHI Grant Number JP 21F21325. R.A.W. acknowledges support from NASA JWST Interdisciplinary Scientist grants NAG5-12460, NNX14AN10G and 80NSSC18K0200 from GSFC. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238. C.M. acknowledges support by the VILLUM FONDEN under grant 37459. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant DNRF140. K.G. and T.N. acknowledge support from Australian Research Council Laureate Fellowship FL180100060.

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Additional details

Identifiers

Eprint ID
121625
Resolver ID
CaltechAUTHORS:20230530-441768000.59

Funding

NASA
NAS 5-03127
Istituto Nazionale di Astrofisica (INAF)
Australian Research Council
CE170100013
Japan Society for the Promotion of Science (JSPS)
JP 21F21325
NASA
NAG5-12460
NASA
NNX14AN10G
NASA
80NSSC18K0200
Slovenian Research Agency
N1-0238
Villum Foundation
37459
Danish National Research Foundation
DNRF140
Australian Research Council
FL180100060

Dates

Created
2023-07-06
Created from EPrint's datestamp field
Updated
2023-07-06
Created from EPrint's last_modified field

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Caltech groups
Infrared Processing and Analysis Center (IPAC)