Dust attenution properties of SFGs at z ∼ 4.5. Left: IRX–β_UV relation derived at 4 < z < 5 by stacking all SFGs with a A³COSMOS coverage (dark-green hexagons) or by stacking all SFGs except the ALMA primary targets (lime-green circles). Hexagons and circles with faded colors correspond to our $⟨L_{\mathrm{UV}}^{\mathrm{phot}.}⟩$ and $⟨{\beta }_{\mathrm{UV}}^{\mathrm{phot}.}⟩$ estimates, i.e., inferred from a COSMOS2020 photometry as opposed to their best-fit SED (see Sect. 4.2). For each stellar mass bin, the fraction of galaxies for which we were able to make such photometric measurement (see text for details) is given in the bottom part of the panel. In parenthesis, we provide the same number but after excluding the ALMA primary targets. The gray shaded squares present measurements for UV-selected SFGs at z ∼ 4 − 8 from Bowler et al. (2024). The black solid, dash-dotted, dashed, and dotted lines show the IRX–β_UV relation observed in local starbursts by Meurer et al. (1999) and by Calzetti et al. (2000), an updated version for local galaxies (Overzier et al. 2011), and an SMC-like dust attenuation relation, respectively. The orange dash-dot-dotted line shows the relation observed in a UV-selected sample of SFGs at z ∼ 4.5 (Fudamoto et al. 2020a). Right: IRX–M_* relation at 4 < z < 5. Symbols are the same as in the left panel. Dark-green and lime-green solid lines are linear fits to these data points, while the associated shaded regions show the 1σ uncertainties on these fits (i.e., the 16th to 84th ranges). The pink dotted line shows the redshift-independent IRX–M_* relation derived by Pannella et al. (2015) for z ≲ 4 SFGs. The black dash-dotted line shows the IRX–M_* relation at z ∼ 4 inferred by Koprowski et al. (2018). The blue dashed line shows the IRX–M_* relation at z ∼ 3 and z ∼ 4.5 found in Fudamoto et al. (2020a,b).