论文标题
极度分散的仙女座XIX矮人银河系的详细星形构成历史
A detailed star formation history for the extremely diffuse Andromeda XIX dwarf galaxy
论文作者
论文摘要
我们从高级摄像头上介绍了超扩散的仙女座XIX XIX DWARF GALAXY的深度成像，以在哈勃太空望远镜上进行调查，该望远镜将其恒星种群解析到最古老的主序列关闭下方。我们使用匹配为银河系提供了完整的星形构成历史，并且在过去的8个GYR中找不到恒星形成的证据。我们计算出$τ_{90} = 9.7 \ pm0.2 $ 〜gyr的淬火时间，建议很早就停止形成星星。这种早期的淬火结合了极大的半灯半径，低密度的暗物质光环和低于预期的金属性，使其成为本地组中的独特星系，并提出了有关其形成方式的疑问。早期的淬火时间使我们能够排除爆发恒星形成的反馈，以此来解释其弥漫性恒星种群和低密度暗物质光环。我们发现，可以通过潮汐相互作用（例如潮汐震动）或晚期干合并来解释延长的恒星种群，低密度光环和恒星形成，后者也解释了其低金属性。适当的动作和详细的丰度将使我们能够区分这两种情况。
We present deep imaging of the ultra-diffuse Andromeda XIX dwarf galaxy from the Advance Camera for Surveys on the Hubble Space Telescope which resolves its stellar populations to below the oldest main sequence turn-off. We derive a full star formation history for the galaxy using MATCH, and find no evidence of star formation in the past 8 Gyr. We calculate a quenching time of $τ_{90}=9.7\pm0.2$~Gyr, suggesting Andromeda~XIX ceased forming stars very early on. This early quenching, combined with its extremely large half-light radius, low density dark matter halo and lower than expected metallicity make it a unique galaxy within the Local Group and raises questions about how it formed. The early quenching time allows us to rule out feedback from bursty star formation as a means to explain its diffuse stellar population and low density dark matter halo. We find that the extended stellar population, low density halo and star formation could be explained by either tidal interactions (such as tidal shocking) or by late dry mergers, with the latter also explaining its low metallicity. Proper motions and detailed abundances would allow us to distinguish between these two scenarios.
