Relation of the characteristic luminosity (upper row) and the slope (lower row) of the Hα luminosity function derived in Virgo (this work), Coma, A1367 (Iglesias-Páramo et al. 2002), and the range of values derived for the field as a function of the total dynamical mass of the clusters (M₂₀₀, from Boselli et al. 2022a, left column), the temperature of the intergalactic medium (central column), and the mean pressure exerted by the intergalactic medium of density ρ_IGM on galaxies moving within it at a velocity V (right column). The temperature of the gas, ρ_IGM, and V are taken from Boselli & Gavazzi (2006). The velocity is the mean velocity of the infalling late-type galaxy population.