Concerted efforts in high-z galaxy evolution in recent years have formed a consistent picture of rising star formation, peaking at z=2 that exponentially decreases until today. Yet, the details of how this transition from a gas-rich, bursty universe to today's largely quiescent one needs an explanation, especially in the light of the evidence for a main sequence of star formation and different feedback properties of galaxies below and above the knee of the mass function.

A better understanding of galaxy formation needs large samples of objects down to the masses of dwarf galaxies:

Using a combination of the wealth of deep (H200A) emission-line galaxies (ELGs) in [OII], [OIII] and H-alpha and estimate equivalent widths (EWs) to produce ELG EW distributions over 0.310^9 for all these lines.

The results agree with theoretical models and complementary observations like narrowband or spectroscopic measurements.
The EW distributions display long tails of extreme equivalent widths for [OIII] and H-alpha and, more surprisingly, very high fractions (up to 30%) of ELGs in the described mass range.
While [OIII] and H-alpha fractions both increase from z=0.3 to z=2, [OII] does not follow this increase, which indicates that a transition in [OIII]/[OII] and ionization parameter is at work at z=2 for these objects.