Probing the Metal Enrichment of the Intergalactic Medium at z = 5–6 Using the Hubble Space Telescope

摘要

We test the galactic outflow model by probing associated galaxies of four strong intergalactic C IV absorbers at z = 5–6 using the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) ramp narrowband filters. The four strong C IV absorbers reside at z = 5.74, 5.52, 4.95, and 4.87, with column densities ranging from NC IV = 10~(13.8) to 10~(14.8) cm~(?2). At z = 5.74, we detect an i-dropout Lyα emitter (LAE) candidate with a projected impact parameter of 42 physical kpc from the C IV absorber. This LAE candidate has a Lyα-based star formation rate (SFRLyα) of 2 Me yr?1 and a UV-based SFR of 4 Me yr?1. Although we cannot completely rule out that this i-dropout emitter may be an [O II] interloper, its measured properties are consistent with the C IV powered galaxy at z = 5.74. For C IV absorbers at z = 4.95 and z = 4.87, although we detect two LAE candidates with impact parameters of 160 and 200 kpc, such distances are larger than that predicted from the simulations. Therefore, we treat them as nondetections. For the system at z = 5.52, we do not detect LAE candidates, placing a 3σ upper limit of SFRLyα ≈ 1.5 Me yr?1. In summary, in these four cases, we only detect one plausible C IV source at z = 5.74. Combining the modest SFR of the one detection and the three nondetections, our HST observations strongly support that smaller galaxies (SFR_(Lyα) ? 2 M⊙ yr~(?1)) are main sources of intergalactic C IV absorbers, and such small galaxies play a major role in the metal enrichment of the intergalactic medium at z ? 5.