Statistics – Computation
Scientific paper
Jul 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dda....38.0803v&link_type=abstract
American Astronomical Society, DDA meeting #38, #8.03
Statistics
Computation
Scientific paper
I present the BEADS-2D code that is designed to study the dynamics of stellar disks in galaxies. An exact description of stellar disks requires the solution of the collisionless Boltzmann equation for the distribution function of stars f(r,u,t) in the phase space (r,u). A general solution of the Boltzmann equation, which is defined in a six-dimensional position and momentum phase space, is usually prohibited due to the large computational expense. However, taking moments of the Boltzmann equation in velocity space turns out to yield a set of equations which is numerically tractable. The BEADS-2D code solves the Boltzmann moment equations up to second order in the thin-disk approximation on a polar grid. The Boltzmann moment equations are closed by the zero-heat-flux approximation, which is equivalent to an assumption of ideal fluid in the classic fluid dynamics approach. The BEADS-2D code directly evolves observable quantities such as stellar surface density, mean stellar velocities, and stellar velocity dispersions (including their cross-correlation term), which makes it advantageous over more common N-body codes. The BEADS-2D code shows an excellent agreement with the predictions of linear stability analysis for stellar disks. I will demonstrate how a spiral structure of any arm multiplicity (including one-armed patterns) can be generated by swing amplification. I will also discuss the influence of the gravitational field of spiral arms onto the shape and orientation (vertex deviation) of stellar velocity ellipsoids within the plane of spiral galaxies. In particular, I will show how the vertex deviation correlates with the position of spiral arms. Other applications of the BEADS code such as the dynamics of planetesimals in debris disks are also possible. A fully three dimensional implementation of the BEADS code is under development. This project was partially supported by RFBR 06-02-16819-a and Federal Agency of Education (project code RNP 2.1.1.3483).
Theis Ch
Vorobyov Eduard
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