How many thick disk subsystems are there in the Milky Way Galaxy?

It was shown that stellar populations of the Galaxy with the thick disk kinematics, namely globular clusters, field RR Lyrae variables (lyrids), and nearby field F - G stars, have different chemical compositions. Based on the analysis of the nature of the dependencies of [alpha/Fe] on [Fe/H] for these objects, it was concluded that the thick disk subsystem in the Galaxy is composite, and at least three components independently exist inside it. The oldest subsystem consists of the metal-rich globular clusters which were formed from a single protogalactic cloud shortly after onset of the explosions of type Ia supernova in it. Then a subsystem of the field thick disk stars was formed as a result of the "heating" of the stars of the primary thin disk already formed in the Galaxy by a rather massive dwarf satellite galaxy which fell onto the Galaxy. And, finally, the subsystem of field stars (including the lyrids) with the kinematics of not only the thick, but even the thin disk that fell onto the Galaxy from this captured satellite galaxy.

Non-linear non-radial oscillations of the self-gravitating disk taking into account halo

In this work, we have studied by numerical methods the evolution of non-radial oscillations of an unsteady disk, which is surrounded by a passive ellipsoidal halo with a uniform density. For this purpose, we have developed a special computer program. Numerical calculations are performed for various values of the system parameters, such as the initial perturbation, the circular speed of rotation of the disk, and the ratio of the halo mass to the disk mass. For each of the possible cases, a statistical amplitude is determined that characterizes the degree of deformation of the system. The critical values of the system parameters are found at which the halo stabilizes the non-linearly non-radial oscillations of the disk subsystem of galaxies at an early stage of their evolution.

The nature of the Galactic bulge: A view from bulge planetary nebulae and globular clusters

Modern data concerning the planetary nebulae (PNe) in the bulge, bar and disk of the Milky Way are used to study the chemical history of bulge. We show that the abundance pattern is similar for PNe in the bulge and Peimbert's type II PNe. We also found that the globular clusters (GCs), especially their metal-rich disk subsystem, form on metallicity maps a bar-like structure which parameters are very close to those for the Galactic bar. These results evidence an old age of the Galactic bulge and bar. We propose a scenario of the successive star formation in the bulge, bar and thin disk.