演講資訊

摘要：

We examine one of the implications of the Lin-Shu spiral density-wave theory, specifically, the noncircular systematic motion of the Galactic objects. The ordinary equations of the Oort-Lindblad theory of galactic differential rotation are used. The minor effects caused by the two-dimensional tightly-wound density waves are also taken into account. The published data of currently known Cepheids, open clusters and HII regions are collected from Ngeow (2008), Dias et al. (2014) and Hou et al. (2014), excluding extremely far, high-velocity, young and old objects in our fitting. The most noteworthy result is the fact that the parameters of density waves estimated from two independent line-of-sight and transversal velocities are nearly equal. We argue that the resemblance of these Galactic wave structures is so remarkable that no doubt is felt as to the theory's truth with respect to these data. The results obtained allow us to conclude that several trailing density-wave patterns with different number of spiral arms, pitch angles and amplitudes of the perturbing gravitational potential may coexist in the Galaxy. The latter suggests the asymmetric multiarm, not well-organized spiral structure of the system under the question.