ON THE INTERPRETATION OF THE HE-II ABSORPTION IN THE LINE-OF-SIGHT OFQ0302-003

We point out the peculiarities of the line of sight of Q0302-003 that was recently used to estimate the He II opacity of the Universe at z s imilar to 3.285 (Jakobsen et al.). This line of sight contains a large void in Lyman alpha clouds, in the region used for the He it opacity observation, and the void is thought to be caused by the ionizing radi ation from a foreground quasar (Dobrzycki & Bechtold). If this is true , then the radiation from the foreground quasar is more relevant in th e region used for the estimation of the He II opacity than the diffuse UV background radiation. We argue that, in that case, the observed op acity should not be used to put a constraint on the diffuse UV backgro und radiation. Using a typical spectral index of quasars, we estimate that most of the observed He II opacity must be due to the Gunn-Peters on effect and suggest an H I Gunn-Peterson test along this line of sig ht. We further discuss the clumpiness of the intergalactic medium in t he vicinity of Q0302-003 as suggested by observations.