The Space Distribution of the Lyman Alpha Clouds in the Line of Sight to the Z=3.66 Qso

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 Lyman lines and metal-line systems for which column densities and Doppler widths have been derived by a tting procedure. The statistical distribution of the Doppler parameter for the Lyman lines is peaked at b ' 23 km s 1, with 13% of lines with 15 b 20 km s 1. The column density distribution of the Lyman lines is described by a power-law with a break or cuto at logNHI ' 14:5. A featureless power-law distribution is rejected with a probability of 99:94%. Signi cant clustering, with ' 1 at v = 100 km s 1, is detected only for lines with logNHI > 13:8. In addition, two voids of size 2000 km s 1 are found in the spectrum with a random probability of 2 10 4. From the proximity e ect for lines in the interval logNHI = 13:3 14:2 it is possible to infer an UV ionizing background J = 5 10 22 ergs s 1 cm 2 Hz 1 sr 1, within a factor of two from the integrated quasar contribution. Subject headings: intergalactic medium { quasars: absorption lines { quasars: individual (0055269)