Abstract
Using recent observational data, we construct a set of multi-component equilibrium models of the disk of a Milky Way-like galaxy. The disk dynamics are studied using collisionless-gaseous numerical simulations, based on the joined integration of the equations of motion for the collision-less particles using direct integration of gravitational interaction and the gaseous SPH-particles. We find that after approximately one Gyr, a prominent central bar is formed having a semi-axis length of about three kpc, together with a multi-armed spiral pattern represented by a superposition of m= 2-, 3-, and 4-armed spirals. The spiral structure and the bar exist for at least 3 Gyr in our simulations. The existence of the Milky Way bar imposes limitations on the density distributions in the subsystems of the Milky Way galaxy. We find that a bar does not form if the radial scale length of the density distribution in the disk exceeds 2.6 kpc. As expected, the bar formation is also suppressed by a compact massive stellar bulge. We also demonstrate that the maximum value in the rotation curve of the disk of the Milky Way galaxy, as found in its central regions, is explained by non-circular motion due to the presence of a bar and its orientation relative to an observer.
Highlights
Attempts to understand the phenomenon of spiral structure in galaxies have a long history [1,2,3,4,5]
We demonstrate that the maximum value in the rotation curve of the disk of the Milky Way galaxy, as found in its central regions, is explained by non-circular motion due to the presence of a bar and its orientation relative to an observer
To model the dynamics of a Milky Way-like collisionless-gaseous disk, we use, for the first time in such a study, direct integration in calculating the gravitational potential, contrary to the approximate tree-code or particle-mesh codes that were used before. It is not clear whether an approximate treatment of the gravity can correctly reproduce the dynamics of the multi-component disks over cosmological time intervals
Summary
Attempts to understand the phenomenon of spiral structure in galaxies have a long history [1,2,3,4,5]. The authors find that the grand design spiral galaxy NGC 1566 shows a significant age gradient across the spiral arms, consistent “with the prediction of a stationary density wave theory”. While an age gradient of the star clusters across the spiral arms in the other two galaxies (M51a and NGC 628) was not confirmed by [14], the authors do suggest that the spiral structure in M51a is a result of tidal interaction. These authors found that a three-armed spiral pattern is generated in the Milky Way disk, and its spiral structure is sustained during at least 3 Gyr. Here, we present the results of three-dimensional simulations of the dynamics of a Milky Way stellar-gaseous disk. We model the dynamics of three-dimensional multicomponent disks using a set of equilibrium models constrained by observational errors and demonstrate that, in most of the models, a multi-armed spiral pattern (a superposition of spirals with different azimuthal wavenumbers) is generated in the disk
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