@article{23115,
  abstract     = {We investigate the association between galaxies and neutral O I absorption systems at z ∼ 6, which trace metalenriched gas during the epoch of reionization. We identify 40 galaxies across six quasar fields, residing in 15
overdensities within 300 kpc of the background sight lines. Five O I absorption systems are associated with five of
these overdensities, yielding a covering fraction of
0.27 0.10
+0.13
within 300 kpc. The absorption occurs beyond typical
virial radii, indicating that the gas traces extended overdensity environments rather than individual galaxy halos,
unlike the z ∼ 0 circumgalactic medium (CGM), which is largely bound to halos. These galaxy-associated
absorbers account for ∼35% of all O I systems seen in blind quasar surveys, implying the remainder arise in
lower-mass galaxies below our detection threshold or in dense neutral intergalactic medium pockets. The CGM
around these galaxies contains ≳ 2 × 106 M⊙ of oxygen, comparable to the interstellar medium oxygen mass of
the galaxies themselves, suggesting that the surrounding environment holds as much metal mass as the galaxies.
All five galaxy-associated systems show significantly higher
log NCII NOI ( / )
ratios than absorbers lacking galaxy
associations. Furthermore, relative abundance ratios ([Si/O], [C/O]) reveal that four of the five exhibit
enrichment patterns consistent with Population III nucleosynthesis at the outskirts of galaxy overdensities. These
rare systems offer a unique window into the role of first-generation stars in shaping the early metal enrichment of
galaxies and their environments.},
  author       = {Higginson, Jack and Bordoloi, Rongmon and Simcoe, Robert A. and Matthee, Jorryt J and Kashino, Daichi and Mackenzie, Ruari and Kramarenko, Ivan and Lilly, Simon J. and Eilers, Anna-Christina and Naidu, Rohan P. and Yue, Minghao},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{EIGER. VIII. First stars signatures in the connection between O I absorption and galaxies in the epoch of reionization}},
  doi          = {10.3847/1538-4357/ae3e81},
  volume       = {999},
  year         = {2026},
}