Baryon density contrast – temperature phase diagrams (for the convenience of plotting we use the density contrast Δ_b = 1 + δ_b rather than the overdensity δ_b). All the gas in the full EAGLE volume is shown in the top left panel, the gas within R₂₀₀ in the top right panel and the gas within the Bisous filaments excluding gas within R₂₀₀ in the bottom left panel. For each temperature and density bin we co-added the mass of particles and divided by the total mass of the full box. We cut the colour scale at 1% level of the maximum value for clarity. The bottom right panel indicates the isomass curves containing 68% of the baryon mass in Bisous filaments excluding R₂₀₀ (blue line), within the outskirts (black line), and within R₂₀₀ (red line). The low-density, low-temperature track seen in the upper left panel corresponds to the photo-heated IGM.