Oxygen and O VII mass fractions within filaments. Left panel: distribution of filamentary oxygen and O VII mass fractions in haloes and the IGM as a function of number density, divided by the total oxygen and O VII mass in the gas phase, respectively. Right panel: cumulative mass fraction within Bisous filaments. The sum of oxygen and O VII mass above a given density was divided by the total (non-stellar) mass of oxygen and O VII in the simulation, respectively. In both panels the solid turquoise (dotted yellow) and dashed purple (dash-dotted black) lines refer to the oxygen (O VII) mass within haloes and IGM in filaments, respectively. The grey shaded area indicates the assumed observational limits, for a path between 1 Mpc (log n ≈ −9) and 10 Mpc (log n ≈ −10) along the line of sight. In both panels we show only the oxygen and O VII distributions within Bisous filaments. The remaining oxygen and O VII are outside the filaments.