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Gas-rich disks in the early universe are highly turbulent and have giantstar-forming clumps. Models suggest the clumps form by gravitationalinstabilities, and if they resist disruption by star formation, then theyinteract, lose angular momentum, and migrate to the center to form a bulge.Here we study the properties of the bulges formed by this mechanism. They areall thick, slowly rotating, and have a high Sersic index, like classicalbulges. Their rapid formation should also give them relatively highalpha-element abundances. We consider fourteen low-resolution models and fourhigh-resolution models, three of which have supernova feedback. All models havean active halo, stellar disk, and gaseous disk, three of the models have apre-existing bulge and three others have a cuspy dark matter halo. All show thesame basic result except the one with the highest feedback, in which the clumpsare quickly destroyed and the disk thickens too much. The coalescence ofmassive disk clumps in the center of a galaxy is like a major merger in termsof orbital mixing. It differs by leaving a bulge with no specific dark mattercomponent, unlike the merger of individual galaxies. Normal supernova feedbackhas little effect because the high turbulent speed in the gas produces tightlybound clumps. A variety of indirect observations support the model, includingclumpy disks with young bulges at high redshift and bulges with relativelylittle dark matter.

Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies