PdBI弧秒漩涡巡天（PAWS）：M51的多相冷气体运动学
The PdBI Arcsecond Whirlpool Survey (PAWS): Multi-phase cold gas kinematic of M51
摘要：
运动学的复杂性和M51在天空中的有利位置使该星系成为测试不同旋臂动力学理论的理想目标。利用新的高分辨率PdBI弧秒漩涡调查（PAWS）数据，我们进行了详细的运动学研究M51的特点和量化的起源和性质的非圆运动。使用由其他几个档案数据集支持的倾斜环分析，我们更新了M51的位置角（PA=（173 +/- 3）度）和倾角（i=（22 +/- 5）度）的估计。高分辨率（40 pc）CO速度场的谐波分解首次显示了M51内盘中存在m=3波的运动学证据，其共转速率为R（CR，m=3）=1.1 +/- 0.1 kpc，速度图为Omega_p（m=3）= 140 km/（s kpc）。这种模式似乎是由核棒激发的，而由m=3模式和主螺旋结构之间的耦合产生的拍频证实了它的密度波性质。我们还观察到一个签名的m=1的模式，这可能是负责在小半径和大半径的M51的不对称性。我们提供了一个简单的方法来估计的螺旋扰动（VSP）的振幅的径向变化归因于不同的模式。主旋臂结构具有<Vsp>=50-70 km/s，而与m=1和m=3模式相关的流动速度通常低2倍。我们在低和高空间分辨率的HI和CO速度场的联合分析表明，原子和分子的气相响应不同的螺旋扰动，由于其不同的垂直分布和发射形态。
英文摘要：
The kinematic complexity and the favorable position of M51 on the sky make this galaxy an ideal target to test different theories of spiral arm dynamics. Taking advantage of the new high resolution PdBI Arcsecond Whirlpool Survey (PAWS) data, we undertake a detailed kinematic study of M51 to characterize and quantify the origin and nature of the non-circular motions. Using a tilted-ring analysis supported by several other archival datasets we update the estimation of M51's position angle (PA=(173 +/- 3) deg) and inclination (i=(22 +/- 5) deg). Harmonic decomposition of the high resolution (40 pc) CO velocity field shows the first kinematic evidence of an m=3 wave in the inner disk of M51 with a corotation at R(CR,m=3)=1.1 +/- 0.1 kpc and a pattern speed of Omega_p(m=3) = 140 km/(s kpc). This mode seems to be excited by the nuclear bar, while the beat frequencies generated by the coupling between the m=3 mode and the main spiral structure confirm its density-wave nature. We observe also a signature of an m=1 mode that is likely responsible for the lopsidedness of M51 at small and large radii. We provide a simple method to estimate the radial variation of the amplitude of the spiral perturbation (Vsp) attributed to the different modes. The main spiral arm structure has <Vsp>=50-70 km/s, while the streaming velocity associated with the m=1 and m=3 modes is, in general, 2 times lower. Our joint analysis of HI and CO velocity fields at low and high spatial resolution reveals that the atomic and molecular gas phases respond differently to the spiral perturbation due to their different vertical distribution and emission morphology.
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