We analyze rest-frame ultraviolet to optical spectra of three z≃7.47 -
7.75 galaxies whose Lyα-emission lines were previously detected with
Keck/MOSFIRE observations, using the JWST/NIRSpec observations from the Cosmic
Evolution Early Release Science (CEERS) survey. From NIRSpec data, we confirm
the systemic redshifts of these Lyα emitters, and emission-line ratio
diagnostics indicate these galaxies were highly ionized and metal poor. We
investigate Lyα line properties, including the line flux, velocity
offset, and spatial extension. For the one galaxy where we have both NIRSpec
and MOSFIRE measurements, we find a significant offset in their flux
measurements (∼5× greater in MOSFIRE) and a marginal difference in
the velocity shifts. The simplest interpretation is that the Lyα
emission is extended and not entirely encompassed by the NIRSpec slit. The
cross-dispersion profiles in NIRSpec reveal that Lyα in one galaxy is
significantly more extended than the non-resonant emission lines. We also
compute the expected sizes of ionized bubbles that can be generated by the
Lyα sources, discussing viable scenarios for the creation of sizable
ionized bubbles (>1 physical Mpc). The source with the highest-ionization
condition is possibly capable of ionizing its own bubble, while the other two
do not appear to be capable of ionizing such a large region, requiring
additional sources of ionizing photons. Therefore, the fact that we detect
Lyα from these galaxies suggests diverse scenarios on escape of
Lyα during the epoch of reionization. High spectral resolution spectra
with JWST/NIRSpec will be extremely useful for constraining the physics of
patchy reionization.Comment: Submitted to ApJ (18 pages, 7 figures, 2 tables