论文标题
仍然与传统的星系进化不一致：超扩散星系蜻蜓的星形史44
Still at Odds with Conventional Galaxy Evolution: The Star Formation History of Ultra-Diffuse Galaxy Dragonfly 44
论文作者
论文摘要
我们基于同时拟合到近粉状光度法和高信噪光学光学光谱法，研究了超扩散星系（UDG）蜻蜓44（df44）的星形恒星历史（SFH）。在拟合观测值时，我们采用了具有灵活的SFH的高级物理模型，并在恒星种群参数之间的退化性背景下讨论了结果。通过以前的恒星形成（类似于文献中的方法），通过重建质量组装历史记录，我们发现DF44的恒星质量的90％占$ z \ sim \ sim 0.9 $（$ \ sim 7.2 $ gyr of of of of of $ z \ sim \ sim \ sim）。相比之下，使用先验，更喜欢集中的恒星形成（如先前对DF44恒星种群的研究所示）表明，DF44早在$ z \ sim 8 $（$ \ sim \ sim 12.9 $ gyr ogo ogo）最早形成。无论DF44是旧的还是很古老的，SFHS都意味着早期的星形形成和快速淬火。该结果以及DF44的大尺寸和证据表明它首次进入昏迷集群中，挑战了UDG形成场景，这些场景是将所有UDG视为与规范矮人群体相邻的模拟。虽然我们的结果无法确认任何特定的形式方案，但我们可以从中得出结论，DF44经历了罕见的淬火事件。
We study the star formation history (SFH) of the ultra-diffuse galaxy (UDG) Dragonfly 44 (DF44) based on the simultaneous fit to near-ultraviolet to near-infrared photometry and high signal-to-noise optical spectroscopy. In fitting the observations we adopt an advanced physical model with a flexible SFH, and we discuss the results in the context of the degeneracies between stellar population parameters. Through reconstructing the mass-assembly history with a prior for extended star formation (akin to methods in the literature) we find that DF44 formed 90 per cent of its stellar mass by $z\sim 0.9$ ($\sim 7.2$ Gyr ago). In comparison, using a prior that prefers concentrated star formation (as informed by previous studies of DF44's stellar populations) suggests that DF44 formed as early as $z\sim 8$ ($\sim 12.9$ Gyr ago). Regardless of whether DF44 is old or very old, the SFHs imply early star formation and rapid quenching. This result, together with DF44's large size and evidence that it is on its first infall into the Coma cluster, challenges UDG formation scenarios from simulations that treat all UDGs as contiguous with the canonical dwarf population. While our results cannot confirm any particular formation scenario, we can conclude from this that DF44 experienced a rare quenching event.
