Oxygen-enhanced Extremely Metal-poor Damped Lyα Systems: A Signpost of the First Stars?

Welsh, Louise; Cooke, Ryan; Fumagalli, Michele; Pettini, Max

Abstract

We present precise abundance determinations of two near-pristine damped Lyα systems (DLAs) to assess the nature of the [O/Fe] ratio at [Fe/H] < −3.0 (i.e., <1/1000 of the solar metallicity). Prior observations indicate that the [O/Fe] ratio is consistent with a constant value, [O/Fe] ≃ +0.4, when −3 < [Fe/H] < −2, but this ratio may increase when [Fe/H] ≲ −3. In this paper, we test this picture by reporting new, high-precision [O/Fe] abundances in two of the most metal-poor DLAs currently known. We derive values of [O/Fe] = +0.50 ± 0.10 and [O/Fe] = +0.62 ± 0.05 for these two z ≃ 3 near-pristine gas clouds. These results strengthen the idea that the [O/Fe] abundances of the most metal-poor DLAs are elevated compared to DLAs with [Fe/H] ≳ −3. We compare the observed abundance pattern of the latter system to the nucleosynthetic yields of Population III supernovae (SNe), and find that the enrichment can be described by a (19–25) M⊙ Population III SN that underwent a (0.9–2.4) × 1051 erg explosion. These high-precision measurements showcase the behavior of [O/Fe] in the most metal-poor environments. Future high-precision measurements in new systems will contribute to a firm detection of the relationship between [O/Fe] and [Fe/H]. These data will reveal whether we are witnessing a chemical signature of enrichment from Population III stars and allow us to rule out contamination from Population II stars.

Citation

Welsh, L., Cooke, R., Fumagalli, M., & Pettini, M. (2022). Oxygen-enhanced Extremely Metal-poor Damped Lyα Systems: A Signpost of the First Stars?. Astrophysical Journal, 929(2), Article 158. https://doi.org/10.3847/1538-4357/ac4503

• Journal Article Type: Article
• Acceptance Date: Dec 18, 2021
• Online Publication Date: Apr 25, 2022
• Publication Date: Apr 20, 2022
• Deposit Date: Jun 8, 2022
• Publicly Available Date: Jun 8, 2022
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 929
• Issue: 2
• Article Number: 158
• DOI: https://doi.org/10.3847/1538-4357/ac4503
• Public URL: https://durham-repository.worktribe.com/output/1201778