2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6455We examine the environment of star-forming galaxies selected in the 2dFGRS. We find that bright star-forming galaxies display a significant deficit of faint neighbours relative to passive galaxies. If a deficit in fainter companions implies a smaller mass halo, data support a scenario predicting star-formation to be suppressed in all systems more massive than 10^{13} M_sun,rather than in clusters only.2 pages, 2 figures, to appear in "Multiwavelength Cosmology", Mykonos Conference ProceedingsAstrophysicstext