Dust properties of XS55. Left: Dust temperature vs. redshift for XS55 and literature samples. The T_d − z relation of main-sequence galaxies from Schreiber et al. (2018) is shown as a black line, with the uncertainty as the shaded grey area. The literature samples are from Riechers et al. (2013, 2014, 2017), Marrone et al. (2018), Pavesi et al. (2018), Faisst et al. (2020), Jin et al. (2019, 2022), Fudamoto et al. (2023), and Algera et al. (2024a,b). The CMB temperature as a function of redshift is shown as a dashed black line. Right: Infrared luminosity surface density as a function of dust temperature, assuming optically thick dust. The surface density limit as defined by the Stefan-Boltzman law of optically thin dust is shown as a black line, while grey-bodies with varying λ_eff are shown as dashed lines. The literature samples are from Simpson et al. (2017), Hodge et al. (2019), and Jin et al. (2019, 2022).