The epochs of bulge and disk formation

M. Samland, G. Hensler
1994 Open Astronomy  
To understand the evolution of galaxies, particularly in the early stages, it is fundamental to investigate the different components of a galaxy and the interactions between them. The number of components and, even more important, the number of processes that account for mass, momentum and energy transfer between the components make it impossible to describe galactic evolution with simple analytical models. Especially in the case of rotating galaxies, a twodimensional hydrodynamical treatment
more » ... necessary. We calculate the eyolution of rotating galaxies using a 2-D hydrodynamical code with five components, i.e., low-mass (LMS), intermediate-mass (IMS) and high-mass stars (HMS), a warm cloudy component with embedded cold clumps (CM) and a hot intercloud medium (ICM). The following interactions are taken into account: condensation, evaporation, cooling and heating of the gas, cloud collisions with dissipation, star formation and stellar mass loss (SN I, SN II and planetary nebulae). Starting with a rigidly rotating protogalactic cloud of 1.5 · 10 11 MQ, which is close to virial equilibrium, the system begins to collapse slowly. Due to the collapse, the density of the CM and, therefore, the star-formation rate (SFR) in the central region of the galaxy increases. In contrast to the cloudy medium, which is gravitationally accelerated towards the center of the galaxy, the hot metal-enriched gas (IMC), ejected by the first SN II, streams out of the central galactic region due to pressure support. In the outer regions, preferably
doi:10.1515/astro-1994-1-218 fatcat:zry246jdpnczfonkz5gxuicggi