发表机构
University of Groningen; Università degli Studi di Firenze; INAF – Osservatorio Astrofisico di Arcetri; Institute of Science and Technology Austria (ISTA); The University of Texas at Austin; University of Chicago（格罗宁根大学; 佛罗伦萨大学; 意大利国家天体物理研究所阿切特里天文台; 奥地利科学与技术研究院; 德克萨斯大学奥斯汀分校; 芝加哥大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究基于JWST NIRSpec光谱，分析了1889个恒星质量跨度4个数量级的星系，发现红移3.5-7.0星系的谱线比率随爆发性变化，高爆发性星系的谱线离散度更高，支持恒星形成爆发产生临时化学增丰的情景。
AI 中文摘要
我们利用JWST NIRSpec光谱的发射线诊断，对1889个恒星质量跨度超过4个数量级的恒星形成源，开展了红移z=3.5-7.0星系物理条件的研究。我们发现，在这些红移范围内，Hα/Hβ和[OIII]/Hβ的中值保持恒定，表明从再电离时代到宇宙正午，星际介质条件演化缓慢。这些谱线比率的恒星质量演化符合化学增丰与尘埃积累的预期趋势：当恒星质量M_⋆≈10^9 M_⊙时，[OIII]/Hβ达到最大值；Hα/Hβ和[OII]/Hβ的中值从恒星质量M_⋆≈10^7 M_⊙到≈10^10 M_⊙单调递增。聚焦于1552个低恒星质量（<10^9 M_⊙）星系，我们特别研究了主要谱线比率随爆发性的变化。我们发现，高爆发性星系的[OIII]/Hβ和[OII]/Hβ的离散度显著高于低爆发性星系；log([OIII]/Hβ)≥0.8几乎仅出现在高爆发性星系中，而log([OIII]/Hβ)≤0.3几乎不会出现在高爆发性星系中，仅在恒星质量log(M_⋆/M_⊙)<7.5的最低质量星系中存在例外。我们的结果支持恒星形成爆发产生临时化学增丰并通过恒星风快速消散的情景，还表明爆发星系的金属量测量不稳定，寻找最贫金属天体应优先在低爆发性或极低恒星质量的源中开展。
英文摘要
We present a study of the physical conditions of galaxies at redshifts $z=3.5-7.0$, based on emission-line diagnostics of JWST NIRSpec spectra for 1889 star-forming sources spanning more than 4~dex in stellar mass. We find that the median H$α$/H$β$ and [OIII]/H$β$ are constant throughout these redshifts, indicating a slow evolution of the interstellar medium conditions from the Epoch of Reionization to Cosmic Noon. The stellar-mass evolution of these line ratios follow the expected trend for chemical enrichment and dust build-up, with \ohb~being maximum for galaxies with $\rm M_{\star} \approx 10^9 \, \rm M_\odot$, and the medians of H$α$/H$β$ and [OII]/H$β$ monotonically increasing from $\rm{M}_{\rm \star} \approx 10^7$ through $ \approx 10^{10}\, \rm M_\odot$. Focusing on the 1552 low stellar-mass ($<10^9 \, \rm M_\odot$) galaxies, we particularly investigate the behaviour of the main spectral-line ratios with burstiness. We find a significantly higher degree of scatter in [OIII]/H$β$ and [OII]/H$β$ for high-burstiness than for low-burstiness galaxies. Values of log([OIII]/H$β$)~$\gtrsim 0.8$ are almost exclusively seen amongst those with high burstiness. Meanwhile, log([OIII]/H$β$)~$\lesssim 0.3$ are virtually not found amongst high-burstiness galaxies, except at the lowest stellar masses $\mathrm{log(M_\star/M_\odot)}<7.5$. Our results are consistent with a scenario in which star-formation bursts produce temporary chemical enrichment that is quickly lost via stellar winds. They also suggest that metallicity measures in bursting galaxies are unstable, and that the search for the most metal-poor objects should optimally be conducted amongst low-burstiness or very low-stellar mass sources.
Comments28 pages, including 1 appendix and 16 figures. Submitted to the ApJ, comments welcome
