Abstract
We explore the expected galaxy environments of CIV absorbers at z>5 using the
Technicolor Dawn simulations. These simulations reproduce the observed history
of reionization, the z~6 galaxy stellar mass function, the Ly\alpha forest
transmission at z>5, and the SiIV column density distribution (CDD) at z=5.5.
Nonetheless, the CIV CDD remains underproduced. Comparison with observed
CII/SiII equivalent width ratios and the CII line incidence suggests that a low
carbon yield accounts for some, but not all, of the CIV discrepancy.
Alternatively, a density-bounded escape scenario could harden the metagalactic
ionizing background more dramatically even than binary stellar evolution,
boosting the CIV CDD into near-agreement with observations. In this case
galaxies ionize more efficiently and fewer are required to host a given
high-ionization absorber. Absorbers' environments therefore constrain ionizing
escape. Regardless of the escape scenario, galaxies correlate with CIV
absorbers out to 300 proper kpc (pkpc). The correlation strengthens
independently with galaxy luminosity and CIV column density. Around strong
systems (log(N_CIV) > 14)), the overdensity of galaxies with M_UV < -18 or
log(L_Ly\alpha) > 41.9 declines from 200-300 within 100 pkpc to 40-60 within
250 pkpc. The previously-suggested association between strong CIV absorbers and
Ly\alpha emitters at z>5 is not expected. It may arise if both populations
inhabit large-scale voids, but for different reasons. Although most neighboring
galaxies are too faint for HST, JWST will, with a single pointing, identify ~10
neighboring galaxies per strong CIV absorber at z>5. Ground-based tests of
these predictions are possible via deep surveys for Ly\alpha emission using
integral field units.
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