Age dating the Galactic bar with the nuclear stellar disc
Age dating the Galactic bar with the nuclear stellar disc
复制标题
DOI：
10.1093/mnras/staa140
复制
发表时间：
2019-09
影响因子：
4.8
通讯作者：
J. Baba;D. Kawata
中科院分区：
文献类型：
--
作者：
J. Baba;D. Kawata
几十年来的理论研究表明，棒的形成触发了气体向中心亚千秒差距区域的汇集，并导致了运动学冷核星盘（NSD）的形成。我们证明，这种机制可以用来识别银河系酒吧的形成时代，使用一个孤立的银河系类星系的N体/流体动力学模拟。正如许多以前的文献所示，我们的模拟表明，棒的形成引发了中心区域1 Gyr的强烈星星形成，并形成了NSD。因此，NSD的最老年龄限制相对尖锐，最老人口变得与酒吧的年龄相似。因此，NSD的年龄分布告诉我们砂坝的形成时代。我们讨论的一个主要挑战，在测量银河系中的NSD的年龄分布是污染的其他不可忽略的恒星组件在中央区域，如一个经典的凸起组件。我们证明，因为NSD是运动学冷比其他恒星人口在银河系中心区域，NSD人口可以从其他恒星人口运动学区分，如果示踪星的三维速度被准确测量。因此，除了光谱测量的视线速度外，还需要精确测量恒星的横向速度，因此，近红外空间天体测量使命JASMINE将在确定银河棒的形成时期方面发挥关键作用。我们还讨论了恒星年龄估计的准确性也是至关重要的NSD恒星人口的最古老的限制措施。
From the decades of the theoretical studies, it is well known that the formation of the bar triggers the gas funnelling into the central sub-kpc region and leads to the formation of a kinematically cold nuclear stellar disc (NSD). We demonstrate that this mechanism can be used to identify the formation epoch of the Galactic bar, using an N-body/hydrodynamics simulation of an isolated Milky Way–like galaxy. As shown in many previous literature, our simulation shows that the bar formation triggers an intense star formation for ∼1 Gyr in the central region and forms an NSD. As a result, the oldest age limit of the NSD is relatively sharp, and the oldest population becomes similar to the age of the bar. Therefore, the age distribution of the NSD tells us the formation epoch of the bar. We discuss that a major challenge in measuring the age distribution of the NSD in the Milky Way is contamination from other non-negligible stellar components in the central region, such as a classical bulge component. We demonstrate that because the NSD is kinematically colder than the other stellar populations in the Galactic central region, the NSD population can be kinematically distinguished from the other stellar populations, if the 3D velocity of tracer stars is accurately measured. Hence, in addition to the line-of-sight velocities from spectroscopic surveys, the accurate measurements of the transverse velocities of stars are necessary, and hence the near-infrared space astrometry mission, JASMINE, would play a crucial role to identify the formation epoch of the Galactic bar. We also discuss that the accuracy of stellar age estimation is also crucial to measure the oldest limit of the NSD stellar population.