The decline in cosmic star formation since z~1: Major mergers or quiescient star formation?

It has been known for a long time, that the cosmic SFR has declined by 3-10 fold since redshift ~1. Since major mergers are effective triggers of star formation and have been more common in the past, it has been argued that the decline is driven by the merger evolution.

Using data from COMBO-17 and GEMS we show that most star formation at z<1 takes place in quiesciently star-forming galaxies, while major mergers are only responsible for a small fraction of the total star formation. Hence, the cosmic decline mostly reflects the decline in normal galaxies and is not driven by major mergers.