Recent results from the  Herschel Space Observatory show that gas-rich galaxies in the early universe were able to create stars at an intense rate.  In the recent universe, we only see such high rates of star formation when galaxies collide.  However, the Herschel data shows that while star-formation in some galaxies in the early universe were triggered by mergers, the majority of star forming galaxies were not undergoing interactions. The formation was driven by the amount of gas present.

via GOODS-Herschel reveals gas mass role in creating fireworks versus beacons of star formation.