DESI EDR中极贫金属恒星形成星系的化学丰度比表征
Characterizing chemical abundance ratios in extremely metal-poor star-forming galaxies in DESI EDR
AI总结：
本文在DESI EDR中识别出21个极贫金属星系，通过直接Te方法测定氧丰度并分析N/O、Ne/O、Ar/O、S/O比值，发现N/O、Ar/O和S/O升高，且J0713+5608可能具有迄今最低的氧丰度。
摘要：
我们展示了对本地宇宙中氧丰度极低星系的一次搜寻，其氧丰度比太阳低25倍以上，对应于12 + log(O/H) < 7.3。为确定氧丰度，我们对检测到[OIII]4363线的天体应用了直接Te方法。我们在暗能量光谱仪（DESI EDR）的早期数据发布中识别出21个极贫金属星系，其中部分星系我们还推导了N/O、Ne/O、Ar/O和S/O比值。我们发现，与从文献中收集的参考低金属丰度样本相比，许多氧丰度极低的DESI星系表现出更高的N/O比值。我们认为N/O比值的升高可以用气体流入或并合事件引起的富金属气体污染来解释。此外，与近期一些研究相反，我们发现Ar/O和S/O比值也同样升高，而Ne/O比值未表现出这种升高。其中一个星系J0713+5608具有极低的氧丰度，为6.978±0.095 dex。这一测量结果与迄今已知的星系最低氧丰度一致。鉴于相对较高的不确定性，该星系可能具有迄今发现的最低氧丰度。此外，与本地宇宙中贫金属星系观测到的典型N/O比值相比，J0713+5608表现出升高的N/O比值。
英文摘要：
We present a search for galaxies in the local Universe with extremely low oxygen abundance, that is, more than 25 times lower than solar, which corresponds to 12 + log(O/H) < 7.3. To determine the oxygen abundance, we apply the direct Te method for objects where the [OIII]4363 line is detected. We identified 21 extremely metal-poor galaxies in the early data release of the Dark Energy Spectroscopic Instrument (DESI EDR), for some of which we also derived N/O, Ne/O, Ar/O, and S/O ratios. We find that many DESI galaxies with extremely low oxygen abundance exhibit a higher N/O ratio in comparison to the reference low-metallicity sample collected from the literature. We suggest that the elevation in N/O ratio may be explained by a contamination with metal-rich gas caused by gas inflow or a merger event. Moreover, contrary to some recent studies, we find that Ar/O and S/O ratios are enhanced as well, while the Ne/O ratio does not show such elevation. One of the galaxies, J0713+5608, has a remarkably low oxygen abundance of 6.978$\pm$0.095 dex. This measurement aligns with the lowest known oxygen abundances in galaxies to date. Given the relatively high uncertainty, this galaxy may have the lowest oxygen abundance ever found. Additionally, J0713+5608 exhibited an enhanced N/O ratio compared to the typical N/O ratio observed in metal-poor galaxies within the local Universe.
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