The formation of disc galaxies in a cosmological context: structure and kinematics

We present results concerning the internal structure and kinematics of diskgalaxies formed in cosmologically motivated simulations. The calculationsinclude dark matter, gas dynamics, radiative cooling, star formation, supernovafeedback and metal enrichment. The initial model is a rigidly rotatingoverdense sphere with a mass of about 8 10^11 Msol which is perturbed by smallscale fluctuations according to a biased CDM power spectrum. Converging, Jeansunstable and rapidly cooling regions are allowed to form stars. Via supernovae,metal enriched gas is returned to the interstellar medium. {}From these initialconditions a galaxy forms which shows the main properties of spiral galaxies: arotationally supported exponential disk which consists of young stars withabout solar metallicity, a slowly rotating halo of old metal poor stars, abulge of old metal rich stars and a slowly rotating extended halo of darkmatter. Bulge, stellar and dark halo are supported by an anisotropic velocitydispersion and have a de Vaucouleurs surface density profile. The flattening ofthe dark and stellar halo is too large to be explained by rotation only.Whether the flattening of the bulge is caused by an anisotropic velocitydispersion or by its rotation cannot be answered, because of the limitednumerical resolution due to gravitational softening. The velocity dispersionand the thickness of the stellar disk increase with the age of the stars.Considering only the young stellar component, the disk is cold (sigma=20km/sec) and thin (z <1 kpc). The dynamical formation process ends after about4\,Gyr, whenComment: 16 pages, compressed uu-encoded postscript file (185kB) no figures, complete compressed postscript file via anonymous ftp deep-thought.MPA-Garching.MPG.DE, pub/Preprints/disk.ps.Z, submitted to MNRAS, Preprint MPA 81