标题： z ~ 7-10处的强巴尔末断裂天体被JWST发现 显示英文标题

标题： Strong Balmer break objects at z ~ 7-10 uncovered with JWST

摘要： 我们报告了发现具有稳健光谱确认的巴尔末断裂（BB）星系和候选者，其可靠的光谱红移$7.1 \le z \le 9.6$来自公开可用的JWST河外光度和光谱调查。为了做到这一点，我们使用了专门探测巴尔末断裂的滤镜，并检查了使用NIRSpec光谱学的对象。我们恢复了之前已知的具有强巴尔末断裂的对象，并揭示了10-11个具有清晰BB的新对象，从而使z >7的光谱确认的BB星系数量翻了三倍。大约一半的星系表现出纯BB且没有近期恒星形成的迹象，而另一半则表现出BB和发射线，表明这些星系的恒星形成可能较早停止并最近重新开始。总体而言，我们发现样本中约10-20%的星系表现出演化恒星种群的特征。此外，我们发现BB的强度并不显著依赖于这些源的静止紫外和静止光学亮度。简而言之，我们的工作证实了仅用测光就有潜力测量BB强度并识别高红移处的演化恒星种群，并且此类物体可能比以前认为的更常见。具有不同断裂强度的星系的存在以及BB和发射线的同时存在表明早期宇宙中的恒星形成具有爆发性。 显示英文摘要

摘要： We report the discovery of robust spectroscopically confirmed Balmer break (BB) galaxies and candidates, with secure spectroscopic redshifts $7.1 \le z \le 9.6$ from publicly available JWST extra-galactic photometric and spectroscopic surveys. To do so, we used dedicated filters probing the Balmer break and inspected the objects with NIRSpec spectroscopy. We recover the previously known objects with strong Balmer breaks and reveal 10-11 new objects with clear BBs, thus tripling the number of spectroscopically confirmed galaxies with a BB at z >7. Approximately half of them show a pure BB and no signs of recent star formation, whereas the other half shows BB and emission lines, indicating most likely galaxies whose star formation ceased earlier and has restarted recently. Overall we find that ~10-20% of all galaxies from our sample show signatures of an evolved stellar population. Furthermore, we find that the strength of the BB does not significantly depend on the rest-UV and rest-optical brightness of these sources. In short, our work confirms that photometry alone has the potential to measure BB strengths and to identify evolved stellar populations at high redshift and that such objects may be more frequent than previously thought. The presence of galaxies with a range of break strengths and the joint presence of BB and emission lines indicate a bursty nature of the star formation in the early Universe.