Reconstructing the Globular Cluster Initial Mass Function from Present-Day Globular Cluster Systems

Abstract

The near-universal turnover mass of the present-day globular cluster mass function (GCMF), $M_{\rm TO} \sim 2 \times 10^5\ {\rm M_\odot}$, is a well established observational feature across galaxies of different types and masses, providing an important empirical benchmark for understanding the globular cluster initial mass function (GCIMF). Competing explanations of this property invoke either dynamical evolution from an initial power-law distribution or an imprint of cluster formation physics. We address this problem by reconstructing the high-mass regime of the GCIMF by inverting the mass loss due to dynamical evolution of present-day globular cluster systems across a wide range of host galaxy masses. Our method is based on an environment-dependent mass-loss model calibrated by direct $N$-body simulations in time-dependent tidal fields, enabling a mapping between observed cluster masses and their progenitor values without assuming a priori a functional form for the GCIMF. We apply our method to galaxies spanning halo masses of $\sim10^{9}$ - $10^{12}\ {\rm M_\odot}$, combining systems with individually measured globular cluster masses as well as large statistical samples constructed from observed global properties. The recovered GCIMFs are systematically shifted towards higher masses and exhibit a power-law behavior at the high-mass end. The inferred slopes vary across galaxies and show a strong correlation with host halo mass, with more massive galaxies exhibiting steeper high-mass slopes. Our results suggest that the slope of the GCIMF depends on the galactic properties and provides a direct empirical link between present-day globular cluster systems and their high-redshift progenitors.