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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 Lyα 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 > 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 > 4.5 show a wide diversity spanning ∼3 orders of magnitude. The metallicities of DLAs at 3.7 < z < 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 sigma) indication of a slight rise in metallicity at 4.5 < z < 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.
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Empirical Constraints on Core-collapse Supernova Yields Using Very Metal-poor Damped Lyα Absorbers
Abstract We place empirical constraints on the yields from zero- and low-metallicity core-collapse supernovae (CCSNe) using abundances measured in very metal-poor (VMP; [Fe/H] ≤ −2) damped Ly α absorbers (DLAs). For some abundance ratios ([N,Al,S/Fe]), VMP DLAs constrain the metal yields of the first SNe more reliably than VMP stars. We compile a large sample of high-S/N VMP DLAs from over 30 yr of literature, most with high-resolution spectral measurements. We infer the initial-mass-function-averaged CCSNe yield from the median values from the DLA abundance ratios of C, N, O, Al, Si, S, and Fe (over Fe and O). We assume that the DLAs are metal-poor enough that they represent galaxies in their earliest stages of evolution, when CCSNe are the only nucleosynthetic sources of the metals we analyze. We compare five sets of zero- and low-metallicity theoretical yields to the empirical yields derived in this work. We find that the five models agree with the DLA yields for ratios containing Si and S. Only one model (Heger & Woosley 2010, hereafter HW10) reproduced the DLA values for N, and one other model (Limongi & Chieffi 2018, hereafter LC18) reproduced [N/O]. We found little change in the theoretical yields with the adoption of an SN explosion landscape (where certain progenitor masses collapse into black holes, contributing no yields) onto HW10, but fixing explosion energy to progenitor mass results in wide disagreements between the predictions and DLA abundances. We investigate the adoption of a simple, observationally motivated initial distribution of rotational velocities for LC18 and find a slight improvement.
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- PAR ID:
- 10335676
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 927
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 64
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3847/1538-4357/ac470e
