S19B0033abst
S19B0033
The primary uncertainty in the claim that cosmic reionization was driven by early star-forming galaxies is how ionizing photons escape from galaxies. To examine the ionizing output and typical fraction fesc that escape, we undertook a deep HST F336W imaging survey of a large sample of z=3 Lyα emitters (LAEs) whose intense [O iii] emission indicates they are useful analogs of galaxies at z>6−7. Surprisingly, we found detected sources have fesc ≃15−60% whereas non-detected sources, even when stacked, reveal no signal at all. Understanding this dichotomy likely holds important clues for understanding how ionizing photons escape. In addition to anisotropic leakage, a possible uncertainty is spatial variations in the opacity of the IGM at z>∼ 3. Accordingly, we have embarked a program to study a comparably-selected sample of z=2.2 Subaru LAEs in the GOODS fields where deep HST UV images are recently available and a similar bimodality in fesc is seen. We request MOSFIRE JHK spectroscopy for a representative sub-sample to physically characterize their properties and verify whether the detections and non-detections are drawn from similar samples where the IGM opacity is unlikely to be significant.
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