Subgalactic Clumps at High Redshift: A Fragmentation Origin?

We investigate the origin of the clumpy structures observed at high redshift,like the chain galaxies. We use a three dimensional chemodynamical simulationdescribing the dynamics of stars and a two-phase interstellar medium, as wellas feedback processes from the stars. For high efficiency of energy dissipationin the cold cloud medium, the initially gaseous disk fragments and developsseveral massive clumps of gas and stars. We follow the evolution of theindividual clumps and determine their masses, metallicities and velocities. Afew dynamical times after fragmentation of the disk, the clumps merge to builda massive bulge. Calculating HST- and UBVRIJHKLM-colors, including absorptionby interstellar dust, we determine the morphologies and colors of this model inHST images. Several peculiar morphological structures seen in the HDF can bewell-explained by a fragmented galactic disk model, including chain galaxiesand objects consisting of several nearby knots.