Distribution and Dynamics of Molecular Gas in the Galaxy M51. III. Kinematics of Molecular Gas
Distribution and Dynamics of Molecular Gas in the Galaxy M51. III. Kinematics of Molecular Gas
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Galaxy M51 中分子气体的分布和动力学。
DOI：
10.1093/pasj/49.3.279
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发表时间：
1997
影响因子：
2.3
通讯作者：
N. Nakai
中科院分区：
文献类型：
--
作者：
N. Kuno;N. Nakai
我们在这里提出了一个研究的分子气体在螺旋星系M51使用CO数据获得的Nobeyama 45米望远镜。从CO气体的径向速度的分布，平行和垂直于螺旋臂的速度分量被确定为每个螺旋相。虽然跨臂的速度分量的变化在质量上与密度波理论一致，但它们的幅度远大于具有小振幅扰动（轴对称场的5-10%）的模型所预测的幅度。通过追踪每个螺旋相的速度矢量，观测确定了CO气体的轨道。轨道偏离很大程度上从纯粹的圆形运动，形成一个椭圆形的模式，从密度波理论的预期。气体表面密度的臂间比可以用这种椭圆运动来解释。此外，在旋臂上的平滑减速和相对于旋臂的对称密度分布都表明在连续流体模型中没有预期的星系激波。
We present here a study of the dynamics of the molecular gas in the spiral galaxy M51 using CO data obtained with the Nobeyama 45-m telescope. From the distribution of the radial velocity of the CO gas, the velocity components parallel and perpendicular to the spiral arms were determined for each spiral phase. Although the variations in the velocity components across the arms are in qualitatively good agreement with density-wave theory, their magnitudes are much larger than those predicted by models with small-amplitude perturbations (5–10% of axisymmetric field). By tracing the velocity vectors at each spiral phase, the orbit of the CO gas was observationally determined. The orbits deviate largely from pure circular motions, forming an oval pattern, as expected from density-wave theory. The arm-to-interarm ratio of the surface density of the gas can be explained in terms of this oval motion. In addition, both the smooth deceleration across the arms and the symmetric density distribution with respect to the arms suggest the lack of the galactic shock expected in a continuous fluid model.