Why are some galaxies brighter than others?

Bright galaxies where stars are forming may outshine dimmer, more massive galaxies. In all previous surveys of the “Redshift Desert,” the brighter star-forming galaxies were the only type bright enough to be sampled. The Gemini Deep Deep Survey was able to sample the dimmer, more massive galaxies and provide a better representation of the galaxies at this epoch of the Universe. The GDDS results revealed that there is a greater abundance of these more massive and older galaxies than expected from current models when the Universe was only 20-40% of its current age.