Comparison between the IR excess (IRX) and the UV spectral slope (β_UV); i.e., the IRX-β_UV relation for HZ10-C, HZ10-W, and the bridge between them. The conventions are as in Fig. 7. Green diamonds correspond to the MASSIVEFIRE sample at z = 6, as included in Liang et al. (2021). The figure also encompasses a series of galaxy samples from the literature: yellow triangles are taken from Heinis et al. (2013), red stars from Álvarez-Márquez et al. (2016), orange stars from Bouwens et al. (2016), blue-edge diamonds from Reddy et al. (2018), magenta-edged circles from McLure et al. (2018), and cyan-edged squares from Fudamoto et al. (2020). The black solid line is the best linear-fit for the IRX-β_UV relation for UV-selected starburst galaxies as shown in Meurer et al. (1999). The light-blue and light-orange shaded areas, as well as the green arrow at the bottom are extracted from the schematic figure included in Popping et al. (2017), which summarizes the different physical mechanisms affecting the properties of the emission sources.