The recent suggestion that a z = 8.3 strongly lensed galaxy system — known as the Firefly Sparkle and observed with JWST earlier this year — is likely the progenitor of a Milky-Way-like galaxy has highlighted the need for detailed, self-consistent modelling of our Galaxy that can connect its present-day properties to those expected at much earlier stages of its life. Elka Rusta and colleagues use semi-analytic models of the Milky Way’s evolution to carry out a discriminating test of this progenitor hypothesis and place new constraints on the physical characteristics of the system.

By building synthetic spectra with the Milky Way evolution model NEFERTITI, the authors show that the most massive galaxy in a Milky Way progenitor system at z ≲ 8 has a 50% probability of being detectable in a typical unlensed JWST survey such as JADES, whilst by z ≲ 7 its detection probability increases to unity. In terms of environment, accounting for lensing magnification means that the number of clumps observed in the Firefly Sparkle is consistent with the authors’ models — indicating that existing JWST data are likely to include other Milky Way progenitor systems we are not yet aware of. The authors also show that their model-predicted photometry agrees with observations, implying star formation histories that are stochastic and bursty.

最近有人提出，一个 z = 8.3 强透镜星系——被称为萤火虫闪光，今年早些时候用 JWST 观测到——很可能是类似银河系的星系的祖先，这凸显了对我们的星系进行详细、自洽建模的需求，该模型可以将其当前的属性与其生命早期阶段的预期属性联系起来。Elka Rusta 及其同事使用银河系演化的半分析模型对这一祖先假说进行了判别性测试，并对系统的物理特性施加了新的约束。

通过使用银河系演化模型 NEFERTITI 构建合成光谱，作者表明，银河系祖先系统中位于 z≲ 8 处的最大质量星系在 z≲ 8 处有 50% 的概率在典型的非透镜 JWST 巡天（如 JADES）中被探测到，而到 z≲ 7 时，它的探测概率增加到统一。在环境方面，考虑透镜放大倍率意味着在 Firefly Sparkle 中观察到的团块数量与作者的模型一致——这表明现有的 JWST 数据可能包括我们尚不了解的其他银河系祖先系统。作者还表明，他们的模型预测的光度学与观测结果一致，这意味着恒星形成历史是随机的和爆发性的。