Evolution of [O II] SB with redshift and stellar mass. Left: Average SB of [O II] emission, corrected for cosmological dimming, in four different redshift bins. The purple circles are for samples that are matched in stellar mass, whereas the orange squares are for samples that are matched in both stellar mass and SFR. Right: Average SB of [O II] emission in four different stellar mass bins. The purple circles are for samples that are matched in redshift, whereas the orange squares are for samples that are matched in both redshift and SFR. In both panels, the filled symbols represent the average values within a circular aperture of radius 20 kpc, and the open symbols the average values within an annular region between radii 20 and 30 kpc.