The spectrum of the QSO Q1159+123 (zem = 3.5) measured using the
high-resolution spectrograph of the Keck 10m telescope, with a resolution
of &lambda/&Delta&lambda = 37000 and
a signal-to-noise ratio of 85 per resolution element. The most prominent
feature is the broad Ly&alpha 1215 emission line near 5500A, blended with
NV 1240 emission at 5600A. The Ly&alpha forest is clearly visible on
the blue side of the Ly&alpha emission line. The absorption features on
the red side are predominantly CIV doublet lines arising from intervening
intergalactic systems containing metals. The rapid decline in flux near
4100A is due to an intervening Lyman Limit System, which absorbs virtually
all photons with energies above the Lyman photoelectric edge (the ionisation
potential of hydrogen). (From Songaila A., 1998, AJ, 115, 2184.)