The space distribution of the Lyman alpha clouds in the line of sight to the z=3.66 QSO 0055-269

The spectrum of the quasar Q0055-269 (z=3.66) has been observed at the resolution of 14 km s^-1 in the wavelength interval 4750-6300 A. We give a list of Lyalpha lines and metal-line systems for which column densities and Doppler widths have been derived by a fitting procedure. The statistical distribution of the Doppler parameter for the Lyalpha lines is peaked at b~=23 km s^-1, with 13 per cent of lines with 15<=b<=20 km s^-1. The column density distribution of the Lyalpha lines is described by a power law with a break or cut-off at log N_HI~=14.5. A featureless power-law distribution is rejected with a probability of 99.94 per cent. Significant clustering, with xi~=1 at Deltav=100 km s^-1, is detected only for lines with log N_HI>~13.8. In addition, two voids of size ~2000 km s^-1 are found in the spectrum with a random probability of 2x10^-4. From the proximity effect for lines in the interval log N_HI=13.3-14.2, it is possible to infer a UV ionizing background J=5x10^-22 erg s^-1 cm^-2 Hz^-1 sr^-1, within a factor of 2 from the integrated quasar contribution.