Distribution of the local environment estimator N_env, defined as the number of companions with M_⋆​ > ​10^7.5 M_⊙ and M_HI​ > ​10⁷ M_⊙ detected within 250 kpc of projected distance and ±500 km s⁻¹ of line-of-sight velocity from the main galaxy, for the MeerKAT (blue histogram) and the TNG50 (orange histogram) galaxy samples. The densely and sparsely hatched histograms show the regular and irregular TNG50 populations, respectively (see Fig. 9).