Reduction in star-forming gas mass in TNG50 cluster satellites after infall. Left: evolution of the star-forming gas mass of the example galaxy of Fig. 3 as a function of lookback time in gigayears. The yellow region shows a clear steep drop in the star-forming gas mass. The solid black line represents the starting point of such a gas drop, which we define as t_drop. The dashed black line represents t_infall as defined in Sect. 2.2.2. The dashed blue, orange, and red lines represent 1 Gyr, 2 Gyr, and 4 Gyr after t_drop, respectively. Middle: relationship between the infall time and the gas drop time for all selected TNG50 cluster satellites: each point represents one galaxy, colored by the mass fraction of star-forming gas in the galaxy at infall. Gray crosses represent preprocessed galaxies that are otherwise excluded from our analysis. The solid black line represents the one-to-one line. Right: probability density distribution of the ratio of remaining star-forming gas mass compared to that at infall, for all the selected TNG50 galaxies inspected 1 Gyr (blue), 2 Gyr (orange), and 4 Gyr after t_drop (red).