Galactic rotation from Cepheids with Gaia DR2 and effects of non-axisymmetry
Galactic rotation from Cepheids with Gaia DR2 and effects of non-axisymmetry
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DOI：
10.1093/mnras/sty2623
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发表时间：
2018-03
影响因子：
4.8
通讯作者：
D. Kawata;J. Bovy;N. Matsunaga;J. Baba
中科院分区：
文献类型：
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作者：
D. Kawata;J. Bovy;N. Matsunaga;J. Baba
我们将简单的轴对称圆盘模型应用于 218 个银河造父变星，通过将现有造父变星目录与 Gaia DR2 数据进行交叉匹配，获得其距离和速度的精确测量。我们的模型拟合确定了“局部离心速度”，$V_\mathrm{c}$ $-$ 定义为平衡太阳位置处的局部径向引力 $-$ 所需的旋转速度为 $V_{c}(R_0)=236\pm 3$ km s$^{-1}$ 以及太阳的方位角和径向特殊运动为分别为$V_{\odot}=12.4\pm0.7$ km s$^{-1}$和$U_{\odot}=7.7\pm0.9$ km s$^{-1}$。这些结果是通过太阳半径 $R_0=8.2\pm0.1$ kpc 和太阳旋转角速度 $\Omega_{\odot}=30.24\pm0.12$ km s$^{-1}$ kpc$^{-1}$ 的强先验获得的。我们还应用轴对称模型来模拟具有条形臂和旋臂的类银河系的 N 体/流体动力学模拟数据。我们发现，即使面对显着的非轴对称性，我们适合年轻恒星的轴对称模型也能很好地恢复局部离心速度。然而，根据我们的造父变星样本确定的局部离心速度可能会受到高达 6 km s$^{-1}$ 的系统不确定性的影响。
We apply a simple axisymmetric disc model to 218 Galactic Cepheids whose accurate measurements of the distance and velocities are obtained by cross-matching an existing Cepheids catalogue with the Gaia DR2 data. Our model fit determines the "local centrifugal speed", $V_\mathrm{c}$ $-$ defined as the rotation speed required to balance the local radial gravitational force $-$ at the Sun's location to be $V_{c}(R_0)=236\pm 3$ km s$^{-1}$ and the Sun's azimuthal and radial peculiar motions to be $V_{\odot}=12.4\pm0.7$ km s$^{-1}$ and $U_{\odot}=7.7\pm0.9$ km s$^{-1}$, respectively. These results are obtained with strong priors on the solar radius, $R_0=8.2\pm0.1$ kpc, and Sun's angular rotation velocity, $\Omega_{\odot}=30.24\pm0.12$ km s$^{-1}$ kpc$^{-1}$. We also applied the axisymmetric model to mock data from an N-body/hydrodynamic simulation of a Milky Way-like galaxy with a bar and spiral arms. We find that our axisymmetric model fit to the young stars recovers the local centrifugal speed reasonably well, even in the face of significant non-axisymmetry. However, the local centrifugal speed determined from our Cepheid sample could suffer from systematic uncertainty as large as 6 km s$^{-1}$.