Subgalactic clumps at high redshift: A fragmentation origin?

We investigate the origin of the clumpy structures observed at high redshift, such as chain galaxies. We use a three-dimensional chemodynamical simulation describing the dynamics of stars and a two-phase interstellar medium, as well as feedback processes from the stars. For high efficiency of energy dissipation in the cold cloud medium, the initially gaseous disk fragments and develops several massive clumps of gas and stars. We follow the evolution of the individual clumps and determine their masses, metallicities, and velocities. A few dynamical times after fragmentation of the disk, the clumps merge to build a massive bulge. Calculating Hubble Space Telescope (HST) and UBVRIJHKLM colors, including absorption by interstellar dust, we determine the morphologies and colors of this model in HST images. Several peculiar morphological structures seen in the Hubble Deep Field can be well explained by a fragmented galactic disk model, including chain galaxies and objects consisting of several nearby knots.