Disk structures and the handiwork of triaxial tumbling dark halos

Abstract. The triaxial and tumbling nature of dark matter halos has been established through cosmological simulations. Such a configuration can then potentially impart a slow-ing changing torque on the galactic disk from outside. We use this idea as the motivation to seek the possible dynamical effects of such a halo in terms of the development of disk structures. To check this effect, we perform a series of N-body simulations and some an-alytical calculations, in which we study the disk configuration, as affected by an imposed, slowly tumbling, external quadrupole. For our simulations, the amplitude of this quadrupole is gauged from a sample of halos that we establish through cosmological, N-body simula-tions. When used as an input, such a quadrupole is found to generate pronounced spirality, long-lived warps and fast bars in model galactic disks that are inherently stable against such instabilities for a long time. Our analytical calculations are found to indicate similar trends in disk stellar motion, as noted in our simulations. Key words. dark matter – galaxies: structure – methods: N-body simulation