Kavli Affiliate: Robert A. Simcoe
| First 5 Authors: Daichi Kashino, Simon J. Lilly, Jorryt Matthee, Ruari Mackenzie, Anna-Christina Eilers
| Summary:
We present a comprehensive analysis of the relationship between galaxies and
the intergalactic medium (IGM) during the late stages of cosmic reionization,
based on the complete JWST EIGER dataset. Using deep NIRCam $3.5,mathrm{mu
m}$ slitless spectroscopy, we construct a sample of 948
[OIII]$lambda5008$-emitting galaxies with $-21.4lesssim
M_mathrm{UV}lesssim -17.2$ spanning $5.33<z<6.97$ along six quasar
sightlines. We correlate these galaxies with Lya and Lyb transmission
measured from high-resolution quasar spectra across multiple redshift
intervals. We find clear redshift evolution in the correlation between galaxy
density and transmission: it is suppressed in overdense regions at $z<5.50$,
while enhanced at $5.70<z<6.15$. The intermediate range exhibits a transitional
behavior. Cross-correlation measurements further reveal excess absorption
within $sim 8$,cMpc of galaxies at low redshifts, and enhanced transmission
at intermediate scales ($sim$5–20,cMpc) at $z>5.70$. Statistical tests using
mock catalogs with realistic galaxy clustering but no correlation with the
transmission field confirm that the observed correlations are unlikely to arise
by chance. The evolving signals can be explained by stronger absorption in
overdense regions, combined with the competing influences of local radiation
fields and the rising background radiation. While local radiation dominates
ionization of the surrounding IGM at earlier times, the background becomes
increasingly important, eventually surpassing the impact of nearby galaxies.
These results support an inside-out progression of reionization, with ionized
regions originating around clustered, star-forming galaxies and gradually
extending into underdense regions.
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