The kinematic signature of the Galactic warp in Gaia DR1 - I. The Hipparcos subsample
The kinematic signature of the Galactic warp in Gaia DR1 - I. The Hipparcos subsample
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DOI：
10.1051/0004-6361/201629916
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
E. Poggio;E. Poggio;R. Drimmel;R. Smart;R. Smart;A. Spagna;M. Lattanzi
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文献类型：
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作者：
E. Poggio;E. Poggio;R. Drimmel;R. Smart;R. Smart;A. Spagna;M. Lattanzi
导致我们银河系翘曲的机制及其动力学性质仍然未知。随着高精度天体测量的出现，新的视野已经打开，以检测与翘曲和限制可能的银河系翘曲形成的情况下的运动学。这一贡献的目的是建立是否第一盖亚数据发布（DR1）显示了显着的运动学特征的证据，预计从一个长寿的银河系弯曲的运动学遥远的OB星。作为系列论文的第一篇，我们提出了分析自行的方法，并将其应用于依巴谷星的子样本。我们选择了一个样本的989遥远的光谱确定OB星的新减少依巴谷，其中758也在盖亚DR1，覆盖距离从0.5至3千秒差距的太阳。我们开发了一个模型的OB星的空间分布和运动学，从我们产生的概率分布函数的自行车，有和没有系统的运动预期从一个长期的翘曲。一个可能性分析是用来比较的预期模型与观察到的自行从依巴谷和盖亚DR1。我们发现，附近的OB星的自行是一致的弯曲的签名，而那些更遥远的恒星（视差<1 mas）不是。我们的年轻OB星样本的运动学表明，在磁盘系统的垂直运动不能解释一个简单的模型，一个稳定的长寿翘曲。银河系的翘曲可能是一个短暂的特征，或者是其他的现象作用于银河系的气体成分，导致系统的垂直运动掩盖了预期的翘曲信号。需要使用盖亚天体测量法获得更大、更深的恒星样本，以限制银河系扭曲的动力学性质。
The mechanism responsible for the warp of our Galaxy, as well as its dynamical nature, continues to remain unknown. With the advent of high precision astrometry, new horizons have been opened for detecting the kinematics associated with the warp and constraining possible warp formation scenarios for the Milky Way. The aim of this contribution is to establish whether the first Gaia data release (DR1) shows significant evidence of the kinematic signature expected from a long-lived Galactic warp in the kinematics of distant OB stars. As the first paper in a series, we present our approach for analyzing the proper motions and apply it to the sub-sample of Hipparcos stars. We select a sample of 989 distant spectroscopically-identified OB stars from the New Reduction of Hipparcos, of which 758 are also in Gaia DR1, covering distances from 0.5 to 3 kpc from the Sun. We develop a model of the spatial distribution and kinematics of the OB stars from which we produce the probability distribution functions of the proper motions, with and without the systematic motions expected from a long-lived warp. A likelihood analysis is used to compare the expectations of the models with the observed proper motions from both Hipparcos and Gaia DR1. We find that the proper motions of the nearby OB stars are consistent with the signature of a warp, while those of the more distant stars (parallax<1 mas) are not. The kinematics of our sample of young OB stars suggests that systematic vertical motions in the disk cannot be explained by a simple model of a stable long-lived warp. The Galactic warp may either be a transient feature, or additional phenomena are acting on the gaseous component of the Milky Way, causing systematic vertical motions that are masking the expected warp signal. A larger and deeper sample of stars with Gaia astrometry will be needed to constrain the dynamical nature of the Galactic warp.