Forming disk galaxies in wet major mergers. I. Three fiducial examples
  Using three fiducial Nbody+SPH simulations, we follow the merging of two disk
galaxies with a hot gaseous halo component each, and examine whether the merger
remnant can be a spiral galaxy. The stellar progenitor disks are destroyed by
violent relaxation during the merging and most of their stars form a classical
bulge, while the remaining form a thick disk and its bar. A new stellar disk
forms subsequently and gradually in the remnant from the gas accreted mainly
from the halo. It is vertically thin and well extended in its equatorial plane.
A bar starts forming before the disk is fully in place, contrary to what is
assumed in idealised simulations of isolated bar-forming galaxies. It has
morphological features such as ansae and boxy/peanut bulges. Stars of different
ages populate different parts of the box/peanut. A disky pseudobulge forms
also, so that by the end of the simulation, all three types of bulges coexist.
The oldest stars are found in the classical bulge, followed by those of the
thick disk, then by those in the thin disk. The youngest stars are in the
spiral arms and the disky pseudobulge. The disk surface density profiles are of
type II (exponential with downbending), and the circular velocity curves are
flat and show that the disks are submaximum in these examples: two clearly so
and one near-borderline between maximum and submaximum. On average, only
roughly between 10 and 20% of the stellar mass is in the classical bulge of the
final models, i.e. much less than in previous simulations.
