  The high redshift galaxy MS1512-cB58 (z=2.724, m_V=20.64) has been observed
with the very efficient high resolution echelle spectrograph VLT/UVES. Although
this is a very challenging observational program for a Southern hemisphere
telescope (the galaxy is located at +36 deg declination), high resolution
spectra (FWHM ~ 26 km/s) have revealed, with unprecedented detail along a
galaxy sight line, the Lyman-alpha forest due to intervening clouds in the
intergalactic medium (IGM). The mean depression D_A due to IGM absorption
blueward of the galaxy Ly-alpha wavelength and the number density dn/dz of
Ly-alpha clouds have been compared with equivalent results obtained for QSO
sight lines at similar redshifts. Our results indicate a possible excess of
absorption close to the galaxy. The mean depression at ~ 150 h_65^-1 Mpc
comoving (Omega_m=0.3, Omega_Lambda=0.7) from the galaxy is D_A=0.36+/-0.03, to
be compared with 0.22+/-0.04, expected from a best fit to QSO sight lines. In
the same region (z=2.610), the number density of lines with HI column density
in excess of 10^14 atoms/cm2 is also about 3 sigma larger than expected. This
high density region is at least 60 h_65^-1 Mpc comoving wide, but the large
Ly-alpha absorption of the galaxy itself prevents us from detecting a possible
structure extending down to the galaxy. This excess of Ly-alpha clouds is
suggestive of two possible scenarios. One is the presence of a super cluster of
Ly-alpha clouds not associated with cB58. The other is a high density of gas
associated with the environment of cB58. Indeed, a hint of the complexity of
cB58 and possibly its environment is given by the huge velocity range (almost
1000 km/s) between the optical emission of star forming regions and UV
absorption of its interstellar medium.
