Physical parameter distributions of the unbiased samples. (a): Logarithmic Lyα luminosity distribution. (b): FWHM distribution of the peak of the Lyα line with the strongest flux. (c): B/T distribution measured on the Lyα emission lines of the double-peaked objects. B/T = 0.5 is represented by a black dash-dotted line. The numbers written in black and orange correspond to the number of galaxies having a B/T value below 0.5 (N = 57 for UDP_I and N = 51 for UDP_R) and above 0.5 (N = 48 for UDP_I and N = 15 for UDP_R). (d): Peak separation distribution of the double-peak samples. In orange are represented the restrictive samples: U ∖ {UDP_R} in dashed lines and UDP_R in solid line. In black are represented the inclusive samples: U ∖ {UDP_I} in dotted lines and UDP_I in solid line.