  We report the first results of a spectroscopic search for Lyman alpha,
envelopes around three z=4.5 radio-quiet quasars. Our observational strategy
uses the FORS2 spectrograph attached to the UT1 of the Very Large Telescope
(VLT) in the multi-slit mode. This allows us to observe simultaneously the
quasars and several PSF stars. The spectra of the latter are used to remove the
point-like quasar from the data, and to unveil the faint underlying Lyman
alpha, envelopes associated with the quasars with unprecedented depth. We
clearly detect an envelope around two of the three quasars. These envelopes
measure respectively 10" and 13" in extent (i.e. 67 kpc and 87 kpc). This is 5
to 10 times larger than predicted by the models of Haiman & Rees (2001) and up
to 100 times fainter. Our observations better agree with models involing a
clumpy envelope as in Alam & Miralda-Escude (2002) or Chelouche et al. (2008).
We find that the brighter quasars also have the brighter envelopes but that the
extend of the envelopes does not depend on the quasar luminosity. Although our
results are based on only two objects with a detected Lyman alpha, envelope,
the quality of the spatial deblending of the spectra lends considerable hope to
estimate the luminosity function and surface brightness profiles of high
redshift Lyman alpha, envelopes down to F= 2-3 10^{-21} erg/s/cm^2/A. We find
that the best strategy to carry out such a project is to obtain both
narrow-band images and deep slit-spectra.
