The impact of galactic winds from Lyman-break galaxies on the intergalactic medium

An excess of sight-lines close to Lyman-break galaxies (LBGs) with little or no absorption in QSO absorption spectra has been reported, and has been interpreted as the effect of galactic winds on the intergalactic medium. We use here numerical simulations to investigate the flux probability distribution function close to plausible sites of LBGs. We show that a model without galactic winds and a model with a wind bubble size of 0.5 h(-1) Mpc (comoving) are consistent with the new determination of the conditional flux distribution by Adelberger et al. Models with the larger bubble sizes (greater than or similar to 1 h(-1) Mpc) suggested by the previous observations of Adelberger et al. based on a much smaller sample at higher redshift are not consistent with the new data. The volume filling factor of galactic winds driven by LBGs may thus be much smaller than previously thought, and most of the metals responsible for the metal absorption associated with the low column density Ly alpha forest appear to be unlikely to have been ejected by LBGs.