On the Formation of Bulges and Elliptical Galaxies in the Cosmological Context

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We study the formation of hot spheroidal systems within the frame of a scenario where galaxy formation and evolution is related to the gentle mass aggregation history and primordial angular momentum of protogalaxies, both defined by the cosmological initial conditions. We explore two cases: (1) the hot spheroidal system forms from the dynamical instabilities of the stellar disks, and (2) the spheroidal systems are formed during the dissipative collapse of the gas before falling to the disk in centrifugal equilibrium. In the former case a good agreement with observations for late type galaxies is found. In the second case, contrary to recent claims, we find that the tidal stability criterion is not easily reached. The gas that dissipatively collapses within the dark matter halos should be very clumpy, and the clumps very dense, in order to avoid the tidal destruction of the star formation unities.