Key points are not available for this paper at this time.
ABSTRACT Strong low-ionization transitions like the Mg ii 2796, 2804 Å doublet are believed to produce a detectable ‘metal-line forest’, if metals pollute the neutral intergalatic medium (IGM). We measure the autocorrelation of the Mg ii forest transmission using 10 ground-based z 6. 80 quasar spectra probing the redshift range 5. 96 z ₌₆\, ₈₈ 7. 42 (z ₌₆\, ₈₈, median = 6. 47). The correlation function exhibits strong small-scale clustering and a pronounced peak at the doublet velocity (v = 768~ km\, s^{-1}) arising from discrete absorbers in the circumgalactic medium of galaxies. After these strong absorbers are identified and masked the signal is consistent with noise. Our measurements are compared to a suite of models generated by combining a large hydrodynamical simulation with a seminumerical reionization topology, assuming a simple uniform enrichment model. We obtain a 95 per cent credibility upper limit of Mg/H -3. 73 at z ₌₆\, ₈₈, median = 6. 47, assuming uninformative priors on Mg/H and the IGM neutral fraction x ₇\, { ₈}. Splitting the data into low-z (5. 96 z ₌₆\, ₈₈ 6. 47; z ₌₆\, ₈₈, median = 6. 235) and high-z (6. 47 z ₌₆\, ₈₈ 7. 42; z ₌₆\, ₈₈, median = 6. 72) subsamples again yields null detections and 95 per cent upper limits of Mg/H -3. 75 and -3. 45, respectively. These first measurements set the stage for making the Mg ii forest an emerging tool to precisely constrain the Universe reionization and enrichment history.
Tie et al. (Tue,) studied this question.