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

Abstract

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 CIV absorption systems at z ̃ 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 (̃80 × 60 h-1 comoving Mpc), we select bright (MUV(1350 Å) ≲ -21.0 mag.) Lyman break galaxies (LBGs) at z ~ 5.7 in a redshift slice Δz ̃ 0.2 and we compare their projected distribution with z ~ 5.7 narrow-band selected Lyman alpha emitters (LAEs, Δz ̃ 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 ̃5 h-1 projected comoving Mpc. In contrast, an excess of LAEs - lower mass galaxies - is found on scales of ̃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 ≲ 3.5), strong C IV absorption systems at z ̃ 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. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.