Observations of chemically enriched QSO absorbers near z ∼ 2.3 galaxies:: Galaxy formation feedback signatures in the intergalactic medium

We present a comparative study of galaxies and intergalactic gas toward the z 2: 73 quasar HS 1700+ 6416, to explore the effects of galaxy formation feedback on the IGM. Our observations and ionization simulations indicate that the volume within 100 - 200 h(71)(-1) 71 physical kpc of high- redshift galaxies is populated by very small ( Delta L less than or similar to 1 kpc), dense ( p/(p) over bar similar to 1000), and metal- rich ( Z greater than or similar to 1/10 - 1/3 Z(circle dot)) absorption- line regions. These systems often contain shockheated gas seen in O (VI) and may exhibit [ Si/ C] abundance enhancements suggestive of preferential enrichment by Type II supernovae. We argue that the absorber geometries resemble thin sheets or bubbles and that their unusual physical properties can be explained using a simple model of radiatively efficient shocks plowing through moderately overdense intergalactic filaments. The high metallicities suggest that these shocks are being expelled from, rather than falling into, star- forming galaxies. There is a drop- off in the intergalactic gas density at galaxy impact parameters of greater than or similar to 300 physical kpc ( greater than or similar to 1 comoving Mpc) that may represent boundaries of the gas structures where galaxies reside. The heavy- element enhancement near galaxies covers smaller distances: at galactocentric radii between 100 and 71 kpc the observed abundances blend into the general metallicity field of the IGM. Our results suggest that either supernova- driven winds or dynamical stripping of interstellar gas alters the IGM near massive galaxies, even at R greater than or similar to 100 kpc. However, only a few percent of the total mass in the Ly alpha forest is encompassed by this active feedback at z similar to 2: 5. The effects could be more widespread if the more numerous metal- poor C (IV) systems at impact parameters >= 200 h(71)(-1) 71 kpc are the tepid remnants of very powerful late- time winds. However, based on present observations it is not clear that this scenario is to be favored over one involving preenrichment by smaller galaxies at z greater than or similar to 6.