¹²C/¹³C for various astronomical environments. The filled red, gray, and white stars represent the ratios derived from the ¹²CO₂ 15.2, 4.27, and 2.70 µm bands, respectively. The closed and open yellow stars represent the ratios derived from the ¹²CO 4.67 and 2.35 µm bands, respectively. The error bars on the JOYS+ data points include the error on the band strengths, which is the main contributor to these uncertainties. The ratios were taken from the following works: Ice age (McClure et al. 2023), (Boogert et al. 2000), KECK-NIRSpec (Boogert et al. 2002a), VLT (Pontoppidan et al. 2003), VLT-CRIRES (Smith et al. 2015), PILS (Jørgensen et al. 2016, 2018), Disks (Yoshida et al. 2022; Bergin et al. 2024), Exo-planets (Line et al. 2021; Zhang et al. 2021a,b; Gandhi et al. 2023; de Regt et al. 2024), Comets (Bockelée-Morvan et al. 2015; Hässig et al. 2017). The dashed purple line shows the solar abundance, and the dot-dashed gray line shows the local ISM ratio (Boogert et al. 2000). Further details of the error analysis can be found in Appendix A.