Detection of star formation in a near-pristine pocket of the Universe

We detect two high-confidence star-forming sources in the environment of a chemically near-pristine ([Fe/H] <-3.66;2σ) Damped Ly α system (DLA) using Keck/KCWI. These are found via the hydrogen Ly α emission line at Δv=-1200 kms-1 (LAE1) and Δv = -200 kms-1 (LAE2) relative to the DLA redshift (z abs = 3.078) at an impact parameter of b=66 physical kpc and b=137 physical kpc. We measure Ly α fluxes of F(Lyα) LAE1 =4.4 plus or minus 0.7 times10-18 erg,s-1,cm-2 and F(Lyα) LAE2 =3.8 plus or minus 0.9 times10-18 erg,s-1,cm-2. This marks the first detection of star formation in the environment of a chemically near-pristine DLA. We use red channel Keck/KCRM data to place limits on the associated He II 1640 A emission flux of these sources, F(He,II)<3.8 times10-19 erg,s-1,cm-2 (3σ) and F(He,II) <3.7 times10-19 erg,s-1,cm-2 (3σ). The weak and narrow properties of the Ly α emission, combined with the inferred position on the mass-metallicity relation, suggest a metal-paucity of these galaxies. Future rest-frame optical observations are required to pin down the metallicity of LAE1 and LAE2 and test if chemically near-pristine DLAs can be used as a signpost to search for primitive, metal-poor galaxies 2 Gyrs after the Big Bang.