Constraints on the Galactic bar from the Hercules stream as traced with RAVE across the Galaxy-猫眼课题宝

DOI：

10.1051/0004-6361/201322623

发表时间：

2013-09

期刊：

Astronomy and Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

T. Antoja;A. Helmi;W. Dehnen;O. Bienaymé;J. Bland-Hawthorn;B. Famaey;K. Freeman;B. Gibson;G. Gilmore;E. Grebel;G. Kordopatis;A. Kunder;I. Minchev;U. Munari;J. Navarro;Q. Parker;W. Reid;G. Seabroke;A. Siebert;M. Steinmetz;F. Watson;R. Wyse;T. Zwitter

银河系位势(旋臂和杆状物)中的非轴对称会产生运动学群，如大力神流。假设大力神是由银河系的外部Lindblad共振效应引起的，我们解析地模拟了它的性质是银河系中位置的函数，以及它对银河系图案速度和方向的依赖。使用RAVE调查的数据，我们发现大力神结构的方位速度作为银心半径的函数而减小，这与我们的分析模型一致。这使我们能够获得对银河系暗条参数的新估计。当图案速度为Ωb=(1.89±0.08)×Ω0时，杆的图案速度和角度的组合似然函数具有最大值，其中Ω0是局部圆形频率。假设太阳半径为8.05kpc，局地圆速度为238公里S-1，则相当于Ωb=56±2公里S-1kpc-1。另一方面，条的方向φb不能用可用数据约束。事实上，似然函数表明在图案速度和方向之间存在紧密的相关性，这意味着线性关系Ωb/Ω0=1.91+0.0044(φb(Deg)-48)更好地描述了我们的最佳拟合结果，标准偏差为0.02。例如，对于φb=30度的角度，图案速度为54.0士0.5kmS-1kpc-1。这些结果对其他银河系参数不是很敏感，如圆周速度曲线或太阳的特殊运动，并且对距离的偏差是稳健的。附录以电子形式在http://www.aanda.org上提供

Non-axisymmetries in the Galactic potential (spiral arms and bar) induce kinematic groups such as the Hercules stream. Assuming that Hercules is caused by the effects of the outer Lindblad resonance of the Galactic bar, we model analytically its properties as a function of position in the Galaxy and its dependence on the bar's pattern speed and orientation. Using data from the RAVE survey we find that the azimuthal velocity of the Hercules structure decreases as a function of Galactocentric radius, in a manner consistent with our analytical model. This allows us to obtain new estimates of the parameters of the Milky Way's bar. The combined likelihood function of the bar's pattern speed and angle has its maximum for a pattern speed of Ωb = (1.89 ± 0.08) × Ω0, where Ω0 is the local circular frequency. Assuming a solar radius of 8.05 kpc and a local circular velocity of 238 km s-1, this corresponds to Ωb = 56 ± 2 km s-1 kpc-1. On the other hand, the bar's orientation φb cannot be constrained with the available data. In fact, the likelihood function shows that a tight correlation exists between the pattern speed and the orientation, implying that a better description of our best fit results is given by the linear relation Ωb/Ω0 = 1.91 + 0.0044(φb(deg) - 48), with standard deviation of 0.02. For example, for an angle of φb = 30 deg the pattern speed is 54.0 ± 0.5 km s-1 kpc-1. These results are not very sensitive to the other Galactic parameters such as the circular velocity curve or the peculiar motion of the Sun, and are robust to biases in distance. Appendices are available in electronic form at http://www.aanda.org

Constraints on the Galactic bar from the Hercules stream as traced with RAVE across the Galaxy

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