The first supernovae and the mass distribution of Population III stars

Sammanfattning: The properties of the early Milky Way are quite mysterious and some are completely unknown even today. This study is the first one ever to analyze the mass distribution of Population III bulge stars. Using the fitting code STARFIT, we perform an analysis of 65 bulge metal-poor stars obtained by the EMBLA survey to estimate the IMF (initial mass function) of the very first stars that defined our galaxy. We report that the determined majority of stars are low mass in the range of 9.6-15 M_Sun. Using the whole sample of stars we first perturb all abundances within their own uncertainties 50 times for each star and obtained the best fitting progenitor mass. Thereafter we carry out 50000 iterations of Monte-Carlo simulations on all obtained masses and calculate the mean masses of the progenitors. Upon fitting an IMF we find that this sample is best described by a power-law function with an exponent alpha = 1.01. By removing masses in the mass range of 15−30 M_Sun we obtain alpha = 2.33, which is almost identical to the one found by Salpeter 1955 and Fraser et al. 2017. The exclusion of these masses is motivated by the fact that an appreciable fraction of the stars in that mass range end their lives by becoming black holes. (Heger and Woosley 2010)