The Diversity of Metal Enrichment and Abundance Patterns at High Redshift: A Magellan Survey of Gas-rich Galaxies Traced by Damped Ly<i>α</i> Absorbers at <i>z</i> ∼ 5

Abstract A powerful technique to trace the signatures of the first stars is through the metal enrichment in concentrated reservoirs of hydrogen, such as the damped Ly α absorbers (DLAs) in the early Universe. We conducted a survey aimed at discovering DLAs along sight lines to high- z quasars in order to measure element abundances at z &gt; 4. Here we report our first results from this survey for 10 DLAs with redshifts of ≈4.2–5.0. We determine abundances of C, O, Si, S, and Fe, and thereby the metallicities and dust depletions. We find that DLA metallicities at z &gt; 4.5 show a wide diversity spanning ∼3 orders of magnitude. The metallicities of DLAs at 3.7 &lt; z &lt; 5.3 show a larger dispersion compared to that at lower redshifts. Combining our sample with the literature, we find a relatively smooth evolution of metallicity with redshift out to z ∼ 5.3, with a tentative (∼2 σ ) indication of a slight rise in metallicity at 4.5 &lt; z &lt; 5.3. The relative abundances exhibit C enhancement for both metal-poor and metal-enriched DLAs. In addition, α -element enhancement is evident in some DLAs, including a DLA at z = 4.7 with a supersolar metallicity. Comparing [C/O] and [Si/O] with model predictions, four DLAs in our survey seem consistent with a nonzero Population III contribution (three with ≳30% Population III contribution). Combining our sample and the literature, we find the dust depletion strength and dust-to-metal ratios to correlate positively with the total (gas+solid phase) metallicity, confirming the presence of metal-rich, dusty DLAs even at ∼1 billion years after the Big Bang.