A dynamical study of three-dimensional spiral galaxies

Luo Xin-Lian, Long Min, Peng Qiu-He, Chou Chi-Kang

Research output: Contribution to journalArticlepeer-review

Abstract

On the basis of a rigorous solution of the three-dimensional (3D) gravitational Poisson equation for density disturbance of logarithmic spiral type, a dispersion relation of 3D mixed disk density wave in the plane of symmetry (z = 0) has been derived. With this result the local stability for disturbed disks of various types is investigated and the group velocity of density waves on the disk surface is calculated. As shown by numerical computations, the logarithmic spiral density disturbance can well satisfy the antiphase relation between the disturbed density and potential. An increase in the thickness or in the number of spiral arms is favourable to the stability of the disk, while a gaseous content may lead to instability. When the effect of thickness is considered, the dynamic time scale of the propagation of density waves in the Galaxy will be very much longer than Toomre's estimate and it may be at least 4.17 × 109 yr, or about one third of the cosmic age. So the problem of too large a group velocity in the previous theories of density waves may be alleviated.

Original languageEnglish
Pages (from-to)159-169
Number of pages11
JournalChinese Astronomy and Astrophysics
Volume25
Issue number2
DOIs
StatePublished - Apr 2001

Keywords

  • Spiral galaxy - galactic dynamics-density waves

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