论文标题
在电离时代的超品种矮人银河eridanus II中，强大的流出和效率低下的恒星形成
Strong Outflows and Inefficient Star Formation in the Reionization-era Ultra-faint Dwarf Galaxy Eridanus II
论文作者
论文摘要
We present novel constraints on the underlying galaxy formation physics (e.g., mass loading factor, star formation history, metal retention) at $z\gtrsim7$ for the low-mass ($M_*\sim10^5$ M$_\odot$) Local Group ultra-faint dwarf galaxy (UFD) Eridanus {\sc II} (Eri II).使用层次结构贝叶斯框架，我们将单区化学演化模型应用于ERI II的基于CAHK的光度法金属分布函数（MDF; [Fe/H]），并发现ERI II的演变由短而指数下降的恒星形成历史记录良好。 （$τ_\ text {sfh} = 0.39 \ pm_ {0.13}^{0.18} $ gyr），低星形效率（$τ_\ text {sfe {sfe {sfe} = 27.56 （$η= 194.53 \ pm_ {42.67}^{33.37} $）。我们的结果与在电源结束之前形成大多数恒星的ERI II一致。较大的质量负载因子意味着在ERI II的早期历史上出现强大的流出，并且与银河风的质量规模的理论预测非常吻合。这也导致$ 90 \％的$ 90 \％在ERI II中生产的金属。我们可以预测[mg/fe] - [fe/h]在ERI II中的分布以及超金属贫困恒星的患病率，这两种恒星都可以通过未来的化学丰度测量值来测试。 ERI II（$ \ text {[Fe/h]}> -2 $）中最高金属性星的光谱随访将大大改善模型约束。我们的新框架可以很容易地应用于整个本地群体的所有UFD，从而提供了对革命时代最微弱星系进化的基本物理学的新见解。
We present novel constraints on the underlying galaxy formation physics (e.g., mass loading factor, star formation history, metal retention) at $z\gtrsim7$ for the low-mass ($M_*\sim10^5$ M$_\odot$) Local Group ultra-faint dwarf galaxy (UFD) Eridanus {\sc II} (Eri II). Using a hierarchical Bayesian framework, we apply a one-zone chemical evolution model to Eri II's CaHK-based photometric metallicity distribution function (MDF; [Fe/H]) and find that the evolution of Eri II is well-characterized by a short, exponentially declining star-formation history ($τ_\text{SFH}=0.39\pm_{0.13}^{0.18}$ Gyr), a low star-formation efficiency ($τ_\text{SFE}=27.56\pm_{12.92}^{25.14}$ Gyr), and a large mass-loading factor ($η=194.53\pm_{42.67}^{33.37}$). Our results are consistent with Eri II forming the majority of its stars before the end of reionization. The large mass-loading factor implies strong outflows in the early history of Eri II and is in good agreement with theoretical predictions for the mass-scaling of galactic winds. It also results in the ejection of $>$90\% of the metals produced in Eri II. We make predictions for the distribution of [Mg/Fe]-[Fe/H] in Eri II as well as the prevalence of ultra metal-poor stars, both of which can be tested by future chemical abundance measurements. Spectroscopic follow-up of the highest metallicity stars in Eri II ($\text{[Fe/H]} > -2$) will greatly improve model constraints. Our new framework can readily be applied to all UFDs throughout the Local Group, providing new insights into the underlying physics governing the evolution of the faintest galaxies in the reionization era.
