Michiko S. Fujii

THE DYNAMICS OF SPIRAL ARMS IN PURE STELLAR DISKS

It has been believed that spirals in pure stellar disks, especially the ones spontaneously formed, decay in several galactic rotations due to the increase of stellar velocity dispersions. Therefore, some cooling mechanism, for example dissipational effects of the interstellar medium, was assumed to be necessary to keep the spiral arms. Here we show that stellar disks can maintain spiral features for several tens of rotations without the help of cooling, using a series of high-resolution three-dimensional

The origin of OB runaway stars.

N

ENRICHMENT OF r-PROCESS ELEMENTS IN DWARF SPHEROIDAL GALAXIES IN CHEMO-DYNAMICAL EVOLUTION MODEL

-body simulations of pure stellar disks. We found that if the number of particles is sufficiently large, e.g.,

BRIDGE: A Direct-Tree Hybrid N -Body Algorithm for Fully Self-Consistent Simulations of Star Clusters and Their Parent Galaxies

3\times 10^6

24.77 Pflops on a gravitational tree-code to simulate the Milky Way Galaxy with 18600 GPUs

, multi-arm spirals developed in an isolated disk can survive for more than 10 Gyrs. We confirmed that there is a self-regulating mechanism that maintains the amplitude of the spiral arms. Spiral arms increase Toomres

KINEMATICS OF CLASSICAL CEPHEIDS IN THE NUCLEAR STELLAR DISK

Q

Dynamical Friction on Satellite Galaxies

of the disk, and the heating rate correlates with the squared amplitude of the spirals. Since the amplitude itself is limited by the value of

The Formation and Dynamical Evolution of Young Star Clusters

Q

The growth of massive stars via stellar collisions in ensemble star clusters

, this makes the dynamical heating less effective in the later phase of evolution. A simple analytical argument suggests that the heating is caused by gravitational scattering of stars by spiral arms, and that the self-regulating mechanism in pure-stellar disks can effectively maintain spiral arms on a cosmological timescale. In the case of a smaller number of particles, e.g.,

The initial mass function of star clusters that form in turbulent molecular clouds

3\times 10^5