BPT diagram. Top panel: emission line ratios in the redshift range z < 0.5 for Flagship (red colour map) compared to SDSS (in grey) main target sample for objects classified as galaxies. Bottom panel: emission line ratio in the redshift range 0.9 < z < 1.8 compared to FMOS stacked data in COSMOS at z ~ 1.5 from Kashino et al. (2019) and MOSFDEF data from Kriek et al. (2015) and Reddy et al. (2015). The black lines are the relations by Kewley et al. (2013a) at z ~ 0 (dotted lines) and z ~ 1.5 (solid lines).