[OII] diagnostic diagram. [OII]/Hβ fux dust-corrected ratios are used. The demarcation lines are taken from Lamareille (2010). Each color represents the trend with stellar mass for a fixed redshift bin: 0.548 < z < 0.632 (blue), 0.632 < z < 0.716 (green), 0.716 < z < 0.8 (purple), and 0.8 < z < 0.884 (red). The total stellar mass increases from left to right. In the left panel, the SDSS galaxies from Vitale et al. (2012) are plotted in gray. The right panel shows a closer view of the zCOSMOS galaxies.