Testing the detectability of supernova ejecta from Population III stars with future ELT/ANDES

Sammanfattning: The first stars, known as Population III (Pop III) stars, formed when the Universe was about 100 Myr to 200 Myr old. In contrast to the present-day Universe, star formation took place in a basically metal-free environment. Despite several decades of research, Pop III stars have not yet been directly observed.  This work investigates the prospects of the ArmazoNes high Dispersion Echelle Spectrograph (ANDES), used with the Extremely Large Telescope (ELT) to observe the supernova ejecta of Pop III stars. If those supernova ejecta enrich a pristine gas cloud, the imprints in the absorption spectrum from a background source may be observable.  First, the prospects of the unique identification of Pop III stars in contrast to non-Pop III stars is studied by using theoretical yields and abundance ratios of supernova simulations. The elements C, O and Si, used in a previous proposal for ANDES, can help to differentiate pair-instability supernovae of Pop III stars from any population and mixture of core-collapse supernovae. The inclusion of N, Al, Mg or Fe supports the discrimination of core-collapse supernovae from different populations.  Second, with a new code to simulate synthetic spectra with resolution and noise relevant for ANDES, the potential to identify a Pop III star is studied. Besides the suggested absorption lines of C, O and Si in the previous ANDES science document, the strong lines of Mg and Fe are potential indicators.