摘要
We present a study of intergalactic medium (IGM) transmission at4.5 < z < 6.5using high-signal-to-noise JWST/NIRSpec prism spectroscopy of 143 galaxies at5<z<7from the CAPERS and JADES surveys. By comparing the observed flux blueward of Ly αemission line to the prediction of spectral energy distribution modeling, we directly measure the IGM transmission along the individual galaxy sightlines. The average transmission measured from these galaxy sightlines is consistent with previous measurements based on luminous quasars. Current NIRSpec spectroscopy is sufficiently deep to probe IGM transmission on single sightlines. We find evidence for a highly ionized structure, atz∼ 5.75-6in the GOODS-S field based on the analysis of a high-S/N spectrum of one galaxy, GS-18846, atz=6.335 . The IGM transmission of GS-z6IS is0.17±0.02 , an order of magnitude higher than the average of previous measurements at this redshift. This structure has a line-of-sight scale of∼110cMpc and spatially extends over at least21×17cMpc ² . GS-z6IS is associated with a known large-scale galaxy overdensity at the same redshift, whose member galaxies show enhanced Ly αvisibility and a broader Ly αequivalent width distribution compared to field galaxies at similar redshift. This result supports the interpretation that Ly αoverdensity can trace bubbles of increased IGM transmission, although environmental effects on galaxy properties may also contribute. Our study demonstrates that high-S/N galaxy spectra offer a powerful new approach to tracing ionized structures during the epoch of reionization.