  We combine a high-resolution hydro-simulation of the LambdaCDM cosmology with
two radiative transfer schemes (for continuum and line radiation) to predict
the properties, spectra and spatial distribution of fluorescent Ly-alpha
emission at z~3. We focus on line radiation produced by recombinations in the
dense intergalactic medium ionized by UV photons. In particular, we consider
both a uniform background and the case where gas clouds are illuminated by a
nearby quasar. We find that the emission from optically thick regions is
substantially less than predicted from the widely used static, plane-parallel
model. The effects induced by a realistic velocity field and by the complex
geometric structure of the emitting regions are discussed in detail. We make
predictions for the expected brightness and size distributions of the
fluorescent sources.Our results account for recent null detections and can be
used to plan new observational campaigns both in the field (to measure the
intensity of the diffuse UV background) and in the proximity of bright quasars
(to understand the origin of high colum-density absorbers).
