High-redshift Lya emitters: clues on the Milky Way infancy

With the aim of determining if Milky Way (MW) progenitors could be identified as high-redshift Lyman Alpha Emitters (LAEs), we have derived the intrinsic properties of z ≈ 5.7 MW progenitors, which are then used to compute their observed Lyα luminosity, Lα, and equivalent width (EW). MW progenitors visible as LAEs are selected according to the canonical observational criterion, Lα > 1042 erg s−1 and EW > 20 Å. Progenitors of MW-like galaxies have Lα = 1039−43.25 erg s−1, making some of them visible as LAEs. In any single MW merger tree realization, typically only one (out of ≈50) progenitor meets the LAE selection criterion, but the probability of having at least one LAE is very high, P = 68 per cent. The identified LAE stars have ages t* ≈ 150–400 Myr at z ≈ 5.7, with the exception of five small progenitors with t* < 5 Myr and large EW = 60–130 Å. LAE MW progenitors provide >10 per cent of the halo very metal-poor stars [Fe/H] < −2, thus establishing a potentially fruitful link between high-z galaxies and the local Universe.