EW₀ (He II) and incidence rate as a function of M_UV for UV bright galaxies, along with other sources. Left: intensity of the He IIλ1640 line for different types of sources: young star clusters and H II regions (green), normal or typical ($L_{\mathrm{UV}}^{\ast }$) Lyman break galaxies (red), and the UV-bright galaxies studied in this work (blue). The R136 cluster and other VMS-source candidates are marked in yellow. Right: incidence of VMS in different galaxy populations: normal LBGs in red and UV-bright galaxies in blue.