arXiv 1507.009072015-07astro-ph.GA

银河系酒吧中高v_los特征的起源

Origin of the high v_los feature in the Galactic bar

Michael Aumer, Ralph Schönrich

备注：: 21 pages, 17 figures, accepted for publication in MNRAS
DOI：: 10.1093/mnras/stv2252

摘要：

我们分析了一个受控的N体+平滑粒子流体动力学模拟的一个不断增长的盘星系内的非增长，活的黑暗晕。圆盘在近圆形的轨道上不断地被气体和恒星粒子供给，并形成了一个大小与银河系（MW）相当的酒吧。我们提取的视线速度v_los分布的模型，并将其与最近获得的数据从APOGEE调查，显示出明显的高速度特征v_los ~ 200 km/s。使用类似于APOGEE的选择函数，但没有任何缩放或调整，我们发现v_los分布与APOGEE中的分布非常相似。构成高v_1os特征的恒星主要是年轻的棒星（年龄<~ 2-3 Gyr），它们沿着棒的后侧远离我们。在负l处，我们发现向我们移动的恒星具有相应的低v_los特征。在l>10度时，最高的v_los星是棒星和背景盘星的混合，这使得观测的解释变得复杂。vlos的主峰主要由前星和背景星所控制。在一个给定的时间，大约40- 50%的高v_los恒星占据类似x_1的轨道，但相当一部分是在更复杂的轨道上。观测到的特征可能是由于动态冷却的年轻恒星群形成于酒吧外面的气体，随后被不断增长的酒吧捕获。高v_los特征在高纬度|b| >~2度处消失，这解释了在其他调查中未检测到这种特征。

英文摘要：

We analyse a controlled N-body + smoothed particle hydrodynamics simulation of a growing disc galaxy within a non-growing, live dark halo. The disc is continuously fed with gas and star particles on near-circular orbits and develops a bar comparable in size to the one of the Milky Way (MW). We extract line of sight velocity v_los distributions from the model and compare it to data recently obtained from the APOGEE survey which show distinct high velocity features around v_los ~ 200 km/s. With an APOGEE like selection function, but without any scaling nor adjustment, we find v_los distributions very similar to those in APOGEE. The stars that make up the high v_los features at positive longitudes l are preferentially young bar stars (age <~ 2-3 Gyr) which move away from us along the rear side of the bar. At negative l, we find the corresponding low v_los feature from stars moving towards us. At l>10 degrees the highest v_los stars are a mixture of bar and background disc stars which complicates the interpretation of observations. The main peak in v_los is dominated by fore- and background stars. At a given time, ~40-50 per cent of high v_los stars occupy x_1 like orbits, but a significant fraction are on more complex orbits. The observed feature is likely due to a population of dynamically cool, young stars formed from gas just outside the bar and subsequently captured by the growing bar. The high v_los features disappear at high latitudes |b|>~2 degrees which explains the non-detection of such features in other surveys.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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英文摘要：

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