Large-scale environment of z ̃ 5.7 C IV absorption systems - I. Projected distribution of galaxies

Metal absorption systems are products of star formation. They are believed to be associated with massive star-forming galaxies, which have significantly enriched their surroundings. To test this idea with high column density C iv absorption systems at z similar to 5.7, we study the projected distribution of galaxies and characterize the environment of C iv systems in two independent quasar lines of sight: J103027.01+052455.0 and J113717.73+354956.9. Using wide-field photometry (similar to 80 x 60 h(-1) comoving Mpc), we select bright (M-UV(1350 angstrom) a parts per thousand(2) -21.0 mag.) Lyman break galaxies (LBGs) at z similar to 5.7 in a redshift slice Delta z similar to 0.2 and we compare their projected distribution with z similar to 5.7 narrow-band selected Lyman alpha emitters (LAEs, Delta z similar to 0.08). We find that the C iv systems are located more than 10 h(-1) projected comoving Mpc from the main concentrations of LBGs and no candidate is closer than similar to 5 h(-1) projected comoving Mpc. In contrast, an excess of LAEs - lower mass galaxies - is found on scales of similar to 10 h(-1) comoving Mpc, suggesting that LAEs are the primary candidates for the source of the C iv systems. Furthermore, the closest object to the system in the field J1030+0524 is a faint LAE at a projected distance of 212 h(-1) physical kpc. However, this work cannot rule out undiscovered lower mass galaxies as the origin of these absorption systems. We conclude that, in contrast with lower redshift examples (z a parts per thousand(2) 3.5), strong C iv absorption systems at z similar to 5.7 trace low-to-intermediate density environments dominated by low-mass galaxies. Moreover, the excess of LAEs associated with high levels of ionizing flux agrees with the idea that faint galaxies dominate the ionizing photon budget at this redshift.