2018/04/16 by Rohan P. Naidu, Ben Forrest, Pascal A. Oesch +4 · 74 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Opacity #Physics #Population #Quantum mechanics #Redshift #Reionization #Star formation #astro-ph.GA
paper · pdf · doi:10.1093/mnras/sty961
published in Monthly Notices of the Royal Astronomical Society 478(1), 791-799 (Oxford University Press) · 10 pages, 8 figures (key result in Figures 7, 8). Accepted for publication in MNRAS. Comments welcome
openalex publication_date 2018/04/16 · arxiv created 2018/04/18 · openalex created_date 2018/04/24 · arxiv updated 2018/05/02 · openalex updated_date 2026/08/05
Recent work has suggested that extreme [O iii] emitting star-forming galaxies are important to reionization. Relatedly, [O iii]/[O ii] has been put forward as an indirect estimator of the Lyman Continuum (LyC) escape fraction (fesc) at z ≳ 4.5 when the opaque IGM renders LyC photons unobservable. Using deep archival U-band (VLT/VIMOS) imaging of a recently confirmed overdensity at z∼ 3.5, we calculate tight constraints on fesc for a sample (N = 73) dominated by extreme [O iii] emitters. We find no LyC signal (|f\rm esc\rm rel < 6.3+0.7-0.7 \hbox per cent| at 1σ) in a deep U-band stack of our sample (31.98 mag at 1σ). This constraint is in agreement with recent studies of star-forming galaxies spanning z ∼ 1–4 that have found very low average fesc. Despite the galaxies in our study having an estimated average rest-frame EW([O iii]λ5007) ∼ 400 Å and [O iii]/[O ii] ∼ 4 from composite SED fitting, we find no LyC detection, which brings into question the potential of [O iii]/[O ii] as an effective probe of the LyC – a majority of LyC emitters have [O iii]/[O ii] > 3, but we establish here that [O iii]/[O ii] > 3 does not guarantee significant LyC leakage for a population. Since even extreme star-forming galaxies are unable to produce the |f\rm esc∼ 10-15\hbox per cent| required by most theoretical calculations for star-forming galaxies to drive reionization, there must either be a rapid evolution of fesc between z∼ 3.5 and the epoch of reionization, or hitherto observationally unstudied sources [e.g. ultrafaint low-mass galaxies with log (M/M⊙) ∼ 7–8.5] must make an outsized contribution to reionization.