The high-redshift signatures of Population III stars

Sammanfattning

The first stars, refereed to as Population III (Pop III), played a very important role in the evolution of the early universe. However, we have yet to observe them. Simulations of Pop III stars show that they likely behave rather differently from the stars we are familiar with today. In this project, we explore how different evolutionary models, specifically including rotation, impact the UV-properties of Pop III stars and the observational consequences of these differences. We find that fast rotation may give rise to a very strong HeIIλ1640 nebular emission line (EW ∼ 100 Å) even for stars with as low masses as 20M⊙. This is in contrast to previous studies that require very top-heavy IMFs (containing stars≥100M⊙) in order to reach such equivalent widths. Consequently, a JWST observation of a Pop III candidate galaxy with such a strong line may not alone be able to constrain the properties of the Pop III IMF and the behaviour of these stars. However, we find that for some parts of the parameter space for Pop III formation, SKA may be sensitive to differences in the 21-cm global signal and power spectrum between a population of rotating and non-rotating Pop III stars.