Boundaries of different conductivity sources in density-temperature space. The red area (k_rad AESOPUS) shows the tabulated region from the AESOPUS2.1 tables (Marigo et al. 2024; Eberlein & Helled 2025), and the dark blue (k_elec FR17) and light blue (k_vib F19) area shows the region with ab initio data points for partially ionized water (French & Redmer 2017; French 2019). The green (k_elec C07) area shows the tabulated electron conductivity as implemented in MESA (Cassisi et al. 2007). Hatched regions with squared lines (k_vib dominated) or dots (k_elec dominated) indicate where k_vib or k_elec contribute more than 50% to the total conductivity assuming the Cond-1 model with Z = 20 for the radiative conductivity. The density temperature regimes around A, B, C, and D are of particular interest and are further discussed in Section 5.