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The Astrophysical journal, 2022-01, Vol.924 (1), p.14
Ort / Verlag
Philadelphia: The American Astronomical Society
Erscheinungsjahr
2022
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
Abstract
Star-forming galaxies are the sources likely to have reionized the universe. As we cannot observe them directly due to the opacity of the intergalactic medium at
z
≳ 5, we study
z
∼ 3–5 galaxies as proxies to place observational constraints on cosmic reionization. Using new deep Hubble Space Telescope rest-frame UV F336W and F435W imaging (30 orbits, ∼40 arcmin
2
, ∼29–30 mag depth at 5
σ
), we attempt to identify a sample of Lyman continuum galaxies (LCGs). These are individual sources that emit ionizing flux below the Lyman break (<912 Å). This population would allow us to constrain cosmic reionization parameters such as the number density and escape fraction (
f
esc
) of ionizing sources. We compile a comprehensive parent sample that does not rely on the Lyman-break technique for redshifts. We present three new spectroscopic candidates at
z
∼ 3.7–4.4 and 32 new photometric candidates. The high-resolution multiband HST imaging and new Keck/Low Resolution Imaging Spectrometer (LRIS) redshifts make these promising spectroscopic LCG candidates. Using both a traditional and a probabilistic approach, we find that the most likely
f
esc
values for the three spectroscopic LCG candidates are >100% and therefore not physical. We are unable to confirm the true nature of these sources with the best available imaging and direct blue Keck/LRIS spectroscopy. More spectra, especially from the new class of 30 m telescopes, will be required to build a statistical sample of LCGs to place firm observational constraints on cosmic reionization.