Messier 33中气体随机运动的各向异性
Anisotropy of random motions of gas in Messier 33
摘要：
我们从邻近星系气体速度色散图研究了各向异性和轴对称速度椭球的性质。这些数据使我们能够测量气体速度椭球的方位径轴比，这是一个有用的工具，研究气体轨道的结构在磁盘。我们还提出了第一个估计的扰动气体速度色散映射应用替代模型，认为各向同性和非对称的随机运动。利用附近螺旋星系Messier 33在不同角分辨率下的原子介质的高质量速度色散图来检验各向异性和各向同性速度模型。还分析了数百个单个分子云的速度色散。M33的HI速度频散沿短轴系统性地较大，沿长轴系统性地较小。各向同性只有在考虑非对称运动时才是可能的。傅立叶变换的HI速度色散揭示了一个bisymmetric模式，这是最强的比其他的非对称运动，并与星系的短轴对齐。在各向异性和轴对称的速度模型中，较强的双对称性被解释为径向分量大于随机运动椭球的方位角分量，因此主要是径向的气体轨道。方位各向异性参数并不强烈依赖于垂直色散的选择。观察到分子云的速度各向异性参数高度分散。像HI螺旋臂这样的扰动可能是M33中气体速度各向异性的起源。进一步的工作是必要的，以评估是否各向异性速度椭球体也可以用来解释其他星系的不对称气体随机运动。
英文摘要：
(Abridged) We study the properties of anisotropic and axisymmetric velocity ellipsoids from maps of the gas velocity dispersion in nearby galaxies. This data allow us to measure the azimuthal-to-radial axis ratio of gas velocity ellipsoids, which is a useful tool to study the structure of gaseous orbits in the disk. We also present the first estimates of perturbations in gas velocity dispersion maps by applying an alternative model that considers isotropic and asymmetric random motions. High-quality velocity dispersion maps of the atomic medium at various angular resolutions of the nearby spiral galaxy Messier 33, are used to test the anisotropic and isotropic velocity models. The velocity dispersions of hundreds of individual molecular clouds are also analyzed. The HI velocity dispersion of M33 is systematically larger along the minor axis, and lower along the major axis. Isotropy is only possible if asymmetric motions are considered. Fourier transforms of the HI velocity dispersions reveal a bisymmetric mode which is mostly stronger than other asymmetric motions and aligned with the minor axis of the galaxy. Within the anisotropic and axisymmetric velocity model, the stronger bisymmetry is explained by a radial component that is larger than the azimuthal component of the ellipsoid of random motions, thus by gaseous orbits that are dominantly radial. The azimuthal anisotropy parameter is not strongly dependent on the choice of the vertical dispersion. The velocity anisotropy parameter of the molecular clouds is observed highly scattered. Perturbations such as HI spiral-like arms could be at the origin of the gas velocity anisotropy in M33. Further work is necessary to assess whether anisotropic velocity ellispsoids can also be invoked to explain the asymmetric gas random motions of other galaxies.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
