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 ($z_{\rm abs} = 3.078$) at an impact parameter of $b=66$ physical kpc and $b=137$ physical kpc. We measure Ly$α$ fluxes of $F(\rm Lyα)_{\rm LAE1} =4.4\pm 0.7\times10^{-18}~\rm erg\,s^{-1}\,cm^{-2}$ and $F(\rm Lyα)_{\rm LAE2} =3.8\pm 0.9\times10^{-18}~\rm erg\,s^{-1}\,cm^{-2}$. 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, $F(\rm He\,II)<3.8\times10^{-19}~\rm erg\,s^{-1}\,cm^{-2}~(3σ)$ and $F(\rm He\,II) <3.7\times10^{-19}~\rm erg\,s^{-1}\,cm^{-2}~(3σ)$. 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.