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The theory of spiral structure of galaxies

Published online by Cambridge University Press:  14 August 2015

L. S. Marochnik
L. S. Marochnik*
Affiliation:
Astrophysical Institute of the Academy of Sciences of the Tadjik S.S.R., Dushanbe, U.S.S.R.

Abstract

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A Landau-type instability mechanism for generating spiral waves is suggested.

Two populations of stars, Populations I and II, are considered, the second one with mean rotational velocity zero. Then a dispersion relation is derived which is reduced to the Lin-Shu dispersion relation in the case of vanishing Population II. The amplification of the wave is of the same type as the two-stream instability. It occurs if the angular velocity of the spiral pattern Ωs is smaller than the angular velocity of the Population I stars. A value of Ωs = 22–25 km s−1 kpc−1 was found, as well as the growth parameter. Spiral arms are formed in 108–109 yr, while trailing and leading waves grow at the same rate.

A quasi-linear theory is developed to account for the limited growth of the spiral waves.

Detailed accounts of the theory and of its implications are contained in recent publications (Marochnik, 1969; Marochnik and Suchkov, 1969a; 1969b; Marochnik and Ptitzina, 1969; Marochnik et al., 1969).

Type
Part III/Theory of Spiral Structure
Information
Symposium - International Astronomical Union , Volume 38: The Spiral Structure of our Galaxy , 1970 , pp. 317
Copyright
Copyright © Reidel 1970 

References

Marochnik, L. S.: 1969, Astrofiz. 15, 487.Google Scholar
Marochnik, L. S. and Suchkov, A. A.: 1969a, Astron. Zh. 46, 319, 524.Google Scholar
Marochnik, L. S. and Suchkov, A. A.: 1969b, Astrophys. Space Sci. 4, 317.Google Scholar
Marochnik, L. S. and Ptitzina, N. G.: 1969, Astron. Zh. 46, 762.Google Scholar
Marochnik, L. S., Pomagaev, S. G., Sagdeev, R. Z., and Suchkov, A. A.: 1969, Dokl. Akad. Nauk S.S.S.R., in press.Google Scholar