2. Dynamical structure of the barred galaxies
In the early 1960s, E. M. and G. R. Burbidge and K. H. Prendergast proposed a
prolate spheroid model of barred galaxies with uniform stellar densities. Another
model was proposed by S. J. Aarseth, who constructed a model consisting of a
spherical central region and cylindrical bars. G. and M. de Vaucoulours showed the
existence of expanding motion of gas in barred galaxies.
Hitotuyanagi’s group considered the two-dimensional motion of gas confined to
the galactic plane in Aarseth’s sphere-cylinder model. The model is shown in
Fig. 5.11, where R 1 and a denote the radii of the central sphere and cylindrical bar,
respectively. R 2 – R 1 is the length of the bar (Aarseth 1960). Under the assumption
that the gas is ejected from the surface of the central sphere at velocity V 0 ,
Fig. 5.10 Formation of spiral arms. Forms of arms at time t in units of 2 Â 10
8 years. (a) t ¼ 1.0,
(b) t ¼ 3.2, (c) t ¼ 5.6, and (d) t ¼ 10.0. (Oki et al. 1965)
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5 Astronomy in Early Showa. III. Sendai 1926–1945