Plot of Hα luminosities versus isophotal area for the galaxies in our sample (red circles). The size of each circle is proportional to the redshift of the galaxy, with larger circles denoting higher redshifts (range in z is 1.3–2.7). The two solid lines show the relationship between luminosity and area for the average surface brightness detection level of galaxies, 1.1 × 10^-17 erg s^-1 cm^-2 arcsec^-2 (black for galaxies at z = 2.2 and red for z = 1.3, respectively). The dot-dashed line shows the relationship for the minimum surface brightness detection limit of 3.6 × 10^-18 erg s^-1 cm^-2 arcsec^-2 for all galaxies with z ≈ 2.2. See Table 1 for the Hα luminosities, isophotal radii and surface brightness detection limits.