******************************************************
   PR # 41134
   To measure the ionized inter-galactic medium in the universe, we
   propose a X-ray Gunn-Peterson test using QSO 4C06.41. A Lyman limit
   system with neutral hydrogen column density 1e17 cm^-2 was found by
   HST in this QSO. The ionized hydrogen column density is expected to
   be 1e23 cm^-2. The purpose of this observation is to detect the
   absorption structure made by neutral heavy elements in the
   inter-galactic medium and to determine the baryon mass in the
   universe.
  ******************************************************