Evolution of space density of CGs obtained in this work (TNG100, dashed red line with circles, shaded regions indicate Poisson errors), by Hartsuiker & Ploeckinger (2020, mock catalogue from EAGLE, dash-dotted green line with squares), and by Sohn et al. (2015, SDSS-DR12, solid blue line with circles). We use vertical dashed black lines to mark four TNG100 snapshots, separated by Δt_cosmic ≈ 1 Gyr. Although at z ≈ 0 the abundances in TNG100 are a factor of ∼2 higher than the observed in SDSS, at higher redshifts the space density of CGs in TNG100 is consistent with that reported by observational works.