Large-scale environment of z ∼ 5.7 C IV absorption systems -II. Spectroscopy of Lyman α emitters

Abstract

The flow of baryons to and from a galaxy, which is fundamental for galaxy formation and evolution, can be studied with galaxy-metal absorption system pairs. Our search for galaxies around C IV absorption systems at z ∼ 5.7 showed an excess of photometric Lyman α emitter (LAE) candidates in the fields J1030+0524 and J1137+3549. Here, we present spectroscopic follow-up of 33 LAEs in both fields. In the first field, three out of the five LAEs within 10h^-1 projected comoving Mpc from the C IV system are within ±500 km s^-1 from the absorption at z_{C IV}=5.7242± 0.0001. The closest candidate (LAE 103027+052419) is robustly confirmed at 212.8^{+14}_{-0.4}h^{-1} physical kpc from the C IV system. In the second field, the LAE sample is selected at a lower redshift (Δz ∼ 0.04) than the C IV absorption system as a result of the filter transmission and, thus, do not trace its environment. The observed properties of LAE 103027+052419 indicate that it is near the high-mass end of the LAE distribution, probably having a large H I column density and large-scale outflows. Therefore, our results suggest that the C IV system is likely produced by a star-forming galaxy which has been injecting metals into the intergalactic medium since z > 6. Thus, the C IV system is either produced by LAE 103027+052419, implying that outflows can enrich larger volumes at z > 6 than at z ∼ 3.5, or an undetected dwarf galaxy. In either case, C IV systems like this one trace the ionized intergalactic medium at the end of cosmic hydrogen reionization and may trace the sources of the ionizing flux density.