D. Elmegreen: Clumpy Galaxies in the Early Universe
By looking at the Hubble Ultra Deep Field (UDF), one can classify galaxies by how they look. The number of clumpy and irregular looking galaxies increases as one looks at further and further distances. Disk galaxies seem to disappear at a certain redshift and only thick disks are found.
Clumpy galaxies seem to be more frequent at high z and it is basically the large star forming regions that are seen there. These clumps should dissolve and could build up a normal spirals. Indeed the "clump clusters" share several properties, altough they are less massive. The scale height of "clump chains" is found to be 1kpc, which could be connected to forming a thick disk.
A usual problem here is that one looks with a fixed set of filters (opitcal in this case), but due to the redshift, one looks at different wavelenths inside the galaxy. In this case, one admittedly only sees the regions that actively form stars and a much smoother underlying population of older stars would not be seen.