Formation of Galactic Bulges

We use cosmological hydrodynamic simulations to investigate formation of galactic bulges within the framework of hierarchical clustering in a representative CDM cosmological model. We show that largest objects forming at cosmological redshifts z ∼ 4 resemble observed bulges of spiral galaxies or moderate size ellipticals in their general properties like sizes, shapes, and density profiles. This is consistent with observational data indicating the existence of “old” bulges and ellipticals at more moderate redshifts. These bulges are gas dominated at redshift z = 3, with high rates of star formation and would appear to be good candidates for small blue galaxies seen in the Hubble Deep Field. Subject headings: cosmology: theory cosmology: large-scale structure of universe galaxies: formation galaxies: intergalactic medium