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Gas-rich disks in the early universe are highly turbulent and have giant star-forming clumps. Models suggest the clumps form by gravitational instabilities, and if they resist disruption by star formation, then they interact, 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 are all thick, slowly rotating, and have a high Sersic index, like classical bulges. Their rapid formation should also give them relatively high alpha-element abundances. We consider fourteen low-resolution models and four high-resolution models, three of which have supernova feedback. All models have an active halo, stellar disk, and gaseous disk, three of the models have a pre-existing bulge and three others have a cuspy dark matter halo. All show the same basic result except the one with the highest feedback, in which the clumps are quickly destroyed and the disk thickens too much. The coalescence of massive disk clumps in the center of a galaxy is like a major merger in terms of orbital mixing. It differs by leaving a bulge with no specific dark matter component, unlike the merger of individual galaxies. Normal supernova feedback has little effect because the high turbulent speed in the gas produces tightly bound clumps. A variety of indirect observations support the model, including clumpy disks with young bulges at high redshift and bulges with relatively little dark matter.
Lenticular galaxies have long been thought of as evolved spirals, but the processes involved to quench the star formation are still unclear. By studying the individual star formation histories of the bulges and disks of lenticulars, it is possible to
We present the results from a study of the morphologies of moderate luminosity X-ray selected AGN host galaxies in comparison to a carefully mass-matched control sample at 0.5 < z < 3 in the CANDELS GOODS-S field. We apply a multi-wavelength morpholo
Recent high-resolution simulations demonstrate that disks around primordial protostars easily fragment in the accretion phase before the protostars accrete less than a solar mass. To understand why the gravitational instability generally causes the f
We analyse stellar masses of clumps drawn from a compilation of star-forming galaxies at 1.1<z<3.6. Comparing clumps selected in different ways, and in lensed or blank field galaxies, we examine the effects of spatial resolution and sensitivity on th
We present a set of bulge-disk decompositions for a sample of 71,825 SDSS main-sample galaxies in the redshift range 0.003<z<0.05. We have fit each galaxy with either a de Vaucouleurs (classical) or an exponential (pseudo-) bulge and an exponential d