Fluorine is one of the most interesting elements for nuclear and stellar astrophysics^1,2. Fluorine abundance was first measured for stars other than the Sun in 1992¹, then for a handful of metal-poor stars³, which are likely to have formed in the early Universe. The main production sites of fluorine are under debate and include asymptotic giant branch stars, the ν-process in core-collapse supernovae, and Wolf–Rayet stars^{4,5,6,7,8,9,10}. Due to the difference in the mass and lifetime of progenitor stars, high-redshift observations of fluorine can help constrain the mechanism of fluorine production in massive galaxies. Here, we report the detection of HF (signal-to-noise ratio of 8) in absorption in a gravitationally lensed dusty star-forming galaxy at redshift z = 4.4 with N_HF/\({N}_{{{{{\rm{H}}}}}_{2}}\) as high as ~2 × 10⁻⁹, indicating a very quick ramp-up of the chemical enrichment in this high-z galaxy. At z = 4.4, asymptotic giant branch stars of a few solar masses are very unlikely to dominate the enrichment. Instead, we show that Wolf–Rayet stars are required to produce the observed fluorine abundance at this time, with other production mechanisms becoming important at later times. These observations therefore provide an insight into the underlying processes driving the ramp-up phase of chemical enrichment alongside rapid stellar mass assembly in a young massive galaxy.

氟是核和恒星天体物理学^1,2最有趣的元素之一。1992 年首次测量了太阳以外恒星的氟丰度¹，然后测量了少数可能在早期宇宙中形成的贫金属恒星^{3 。}氟的主要产生地点正在争论中，包括渐近巨分支星、核心坍缩超新星中的ν过程和沃尔夫-拉叶星^{4,5,6,7,8,9,10}. 由于前身星的质量和寿命不同，对氟的高红移观测可以帮助限制大质量星系中氟产生的机制。在这里，我们报告了在红移z  = 4.4 且N _HF / \({N}_{{{{{\ rm{H}}}}}_{2}}\）高达~2 × 10 ^{-9 ，表明这个高}z星系中的化学富集非常迅速。在z = 4.4，几个太阳质量的渐近巨星分支恒星不太可能主导富集。相反，我们表明此时需要 Wolf-Rayet 星来产生观察到的氟丰度，而其他产生机制在以后变得重要。因此，这些观察结果提供了对推动化学富集加速阶段以及年轻大质量星系中快速恒星质量组装的潜在过程的洞察。