Bandshifting and other Masks of the Clumpy Populations in High Redshift Galaxies

Galaxies observed at high redshift give a biased view of their structures, clump masses, clump ages, and surface densities as a result of bandshifting, angular resolution limitations, and surface brightness dimming. These biases produce trends with redshift, but they are not likely to affect our impression that young galaxies are intrinsically more clumpy than modern galaxies. The clumps probably originate as gravitational instabilities in gas-rich, turbulent disks. The origin of the high gas fractions is not known: they could result from mergers or from rapid cosmological infall.