Distribution of q_TIR with redshift. The gray points show the Radio Sources Sample in the GOODS-N and COSMOS/UltraVISTA fields (see details in Sect. 2). The blue points represent the ${\overline{q}}_{\mathrm{TIR}}$ values of SFGs, which are shown in Fig. 3 and in Sect. 4.1. The blue dashed line represents the best-fit model to the data of SFGs, while the shaded blue region is the associated 1σ uncertainty of the best-fit model. The green dash-dotted line represents the best-fit model from Magnelli et al. (2015) using data in the GOODS-N, GOODS-S, ECDFS, and COSMOS fields. Both the red dotted line (Delhaize et al. 2017) and the yellow dash-dotted line (Novak et al. 2017) represent the best-fit model obtained with the VLA-COSMOS 3 GHz project but using different source selection criteria. The dark red dash-dotted line represents the best-fit model from Enia et al. (2022) based on data from the GOODS-N field. The black star represents the q_TIR value for SFGs in the local universe from Bell (2003).