We present an absorption line analysis of the Lyman limit system ( LLS ) at z \approx 3.55 in our Magellan/MIKE spectrum of PKS2000 - 330 .
Our analysis of the Lyman limit and full H i Lyman series constrains the total H i column density of the LLS ( N _ { HI } = 10 ^ { 18.0 \pm 0.25 } { cm ^ { -2 } } for b _ { HI } \geq 20 { km s ^ { -1 } } ) and also the N _ { HI } values of the velocity subsystems comprising the absorber .
We measure ionic column densities for metal-line transitions associated with the subsystems and use these values to constrain the ionization state ( > 90 \% ionized ) and relative abundances of the gas .
We find an order of magnitude dispersion in the metallicities of the subsystems , marking the first detailed analysis of metallicity variations in an optically thick absorber .
The results indicate that metals are not well mixed within the gas surrounding high z galaxies .
Assuming a single-phase photoionization model , we also derive an N _ { H } -weighted metallicity , < [ Si / H ] > = -1.66 \pm 0.25 , which matches the mean metallicity in the neutral ISM in high z damped Ly \alpha systems ( DLAs ) .
Because the line density of LLSs is over 10 \times higher than the DLAs , we propose that the former dominate the metal mass-density at z \sim 3 and that these metals reside in the galaxy/IGM interface .
Considerations of a multi-phase model do not qualitatively change these conclusions .
Finally , we comment on an anomalously large O ^ { 0 } /Si ^ { + } ratio in the LLS that suggests an ionizing radiation field dominated by soft UV sources ( e.g .
a starburst galaxy ) .
Additional abundance analysis is performed on the super-LLS systems at z \approx 3.19 .