Random selection of 30 SPH particles chosen from those having the origin “cooling CGM, outflowing,” “cooling CGM, inflowing,” “from disk,” and “from satellites.” The backtracking starts from z ≃ 0.3 Left column: trajectory of the selected particles in a 2D plane, following them from z ≃ 0.5 to z ≃ 0.3. The dots become smaller and fainter going back in time, and the color is red and blue when the temperature is respectively higher and lower than 3 × 10⁴. Right column: radial distance from the center of the halo of each particle as a function of redshift.