The giants that were born swiftly – implications of the top-heavy stellar initial mass function on the birth conditions of globular clusters

Abstract

ABSTRACT Recent results suggest that the initial mass function (IMF) of globular clusters (GCs) is metallicity and density dependent. Here, it is studied how this variation affects the initial masses and the numbers of core-collapse supernovae (CCSNe) required to reproduce the observed iron spreads in GCs. The IMFs of all of the investigated GCs were top-heavy implying larger initial masses compared to previous results computed assuming an invariant canonical IMF. This leads to more CCSNe being required to explain the observed iron abundance spreads. The results imply that the more massive GCs formed at smaller Galactocentric radii, possibly suggesting in situ formation of the population II halo. The time until star formation ended within a proto-GC is computed to be 3.5–4 Myr, being slightly shorter than the 4 Myr obtained using the canonical IMF. Therefore, the impact of the IMF on the time for which IMF lasts is small.