Fast radio bursts (FRBs) are millisecond-duration events detected from beyond the Milky Way. FRB emission characteristics favour highly magnetized neutron stars, or magnetars, as the sources¹, as evidenced by FRB-like bursts from a galactic magnetar^2,3, and the star-forming nature of FRB host galaxies^4,5. However, the processes that produce FRB sources remain unknown⁶. Although galactic magnetars are often linked to core-collapse supernovae (CCSNe)⁷, it is uncertain what determines which supernovae result in magnetars. The galactic environments of FRB sources can be used to investigate their progenitors. Here, we present the stellar population properties of 30 FRB host galaxies discovered by the Deep Synoptic Array (DSA-110). Our analysis shows a marked deficit of low-mass FRB hosts compared with the occurrence of star formation in the Universe, implying that FRBs are a biased tracer of star formation, preferentially selecting massive star-forming galaxies. This bias may be driven by galaxy metallicity, which is positively correlated with stellar mass⁸. Metal-rich environments may favour the formation of magnetar progenitors through stellar mergers^9,10, as higher-metallicity stars are less compact and more likely to fill their Roche lobes, leading to unstable mass transfer. Although massive stars do not have convective interiors to generate strong magnetic fields by dynamo¹¹, merger remnants are thought to have the requisite internal magnetic-field strengths to result in magnetars^11,12. The preferential occurrence of FRBs in massive star-forming galaxies suggests that a core-collapse supernova of merger remnants preferentially forms magnetars.

快速射电暴 （FRB） 是从银河系之外探测到的毫秒级事件。FRB 发射特性有利于将高度磁化的中子星或磁星作为源¹，银河系磁星的类似 FRB 的爆发^2,3 和 FRB 宿主星系的恒星形成性质^4,5 证明了这一点。然而，产生 FRB 源的过程仍然未知⁶。尽管银河系磁星通常与核心坍缩超新星 （CCSNe^）7 有关，但不确定是什么决定了哪些超新星会产生磁星。FRB 源的星系环境可用于研究它们的祖先。在这里，我们展示了由深天气阵列 （DSA-110） 发现的 30 个 FRB 宿主星系的恒星种群特性。我们的分析表明，与宇宙中恒星形成的发生相比，低质量 FRB 宿主明显不足，这意味着 FRBs 是恒星形成的偏向示踪剂，优先选择大质量恒星形成星系。这种偏差可能是由星系金属丰度驱动的，它与恒星质量⁸ 呈正相关。富含金属的环境可能有利于通过恒星合并形成磁星祖先^9,10，因为金属丰度较高的恒星不太紧凑，更有可能填满它们的罗氏裂片，从而导致不稳定的质量传递。尽管大质量恒星的内部没有对流来产生发电机¹¹ 产生的强磁场，但合并残余物被认为具有产生磁星所需的内部磁场强度^11,12。FRBs 在大质量恒星形成星系中的优先出现表明，合并残余物的核心坍缩超新星优先形成磁星。