Gas in Galaxies and the Intergalactic Medium at High Redshifts

Wallace Sargent
California Institute of Technology

We review ongoing work on the physical state of gas in the intergalactic
medium and galaxy halos at high redshifts. The topics covered include the
evolution of the ionizing spectrum with redshift, the search for O VI
absorption lines produced by photo- and collisionally-ionized gas, the
micro-structure of gaseous halos and the Lyman alpha forest deduced from
observations of the separate components of gravitationally lensed quasars,
and the evolution of the Lyman alpha forest.