High redshift Lya emitters: clues on the Milky Way infancy

TL;DR

This study investigates whether Milky Way progenitors at high redshift could be observed as Lyman Alpha Emitters (LAEs), analyzing their properties and the likelihood of detection, and linking early galaxy formation to present-day stellar populations.

Contribution

It provides the first detailed modeling of MW progenitors as high-z LAEs, including their luminosity, equivalent width, and the probability of detection, connecting early galaxy properties to local universe observations.

Findings

Some MW progenitors meet LAE criteria at z ~ 5.7.

High probability (68%) of detecting at least one LAE progenitor.

LAE progenitors contribute significantly to very metal-poor stars in the halo.

Abstract

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 Lyman-alpha luminosity, L_alpha, and equivalent width, EW. MW progenitors visible as LAEs are selected according to the canonical observational criterion, L_alpha > 10^42 erg/s and EW > 20 A. Progenitors of MW-like galaxies have L_alpha = 10^(39-43.25) erg/s, making some of them visible as LAEs. In any single MW merger tree realization, typically only 1 (out of ~ 50) progenitor meets the LAE selection criterion, but the probability to have at least one LAE is very high, P = 68%. 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 A. LAE MW progenitors provide > 10% of the halo very metal-poor stars [Fe/H] < -2, thus establishing a potentially fruitful link between high-z galaxies and the Local Universe.