Density-weighted projection of the gas density (left panels), of the gas tracer density (centre panels), and of their relative difference (right panels) along the x axis around the most massive galaxy of the cosmological simulation at z = 2. Top panels: large-scale structure of the gas; data have been selected within 200 kpc of the centre. Bottom panels: zoom on the central galaxy; data have been selected within 10 kpc of the centre of the galaxy. The MC tracer density is similar to that of the gas. The radial modulations are due to differences in cell mass at fixed cell resolution: massive cells (closer to the centre at fixed resolution) are best sampled by the MC tracers.