Small-scale structure at high redshift. III. The clumpiness of the intergalactic medium on subkiloparsec scales

Spectra obtained with the Keck HIRES instrument of the Ly alpha forests in the lines of sight to the A and C components of the gravitationally lensed quasi-stellar object Q1422+231 were used to investigate the structure of th e intergalactic medium at mean redshift [z] similar to 3.3 on subkiloparsec scales. We measured the cross-correlation amplitude between the two Ly alp ha forests for a mean transverse separation of 120 h(50)(-1) pc and compute d the rms column density and velocity differences between individual absorp tion systems seen in both lines of sight. The rms differences between the v elocity centroids of the Ly alpha forest lines were found to be less than a bout 400 ms(-1) for unsaturated H I absorption lines with column densities in the range 12 < log N(H I) < 14.13. The rate of energy transfer into the low-density intergalactic medium on a typical scale of 100 pc seems to be l ower by 3-4 orders of magnitude than the rate measured earlier for strong C IV metal absorption systems. The tight correlation between H I column dens ity and baryonic density in the intergalactic medium was used to obtain a c onservative upper limit on the rms fluctuations of the baryonic density fie ld at [z] = 3.26, namely, [[(Delta log rho)(2)]](1/2) less than or equal to 3.1 x 10(-2) on a scale of 110 h(50)(-1) pc. The fraction of the absorptio n lines that are different across the lines of sight was used to determine the filling factor of the universe for gas that has suffered recent hydrody namic disturbances. We thereby derived upper limits on the filling factor o f galactic outflows at high redshift. Short-lived, short-range ancient wind s are essentially unconstrained by this method, but strong winds blowing fo r a substantial fraction of a Hubble time (at z = 3.3) appear to fill less than 20% of the volume of the universe.