Inverting the dynamical evolution of globular clusters: clues to their origin

Abstract

Abstract. Scaling relations for globular clusters (GCs) differ from scaling relations for pressure supported (elliptical) galaxies. We show that two-body relaxation is the dominant mechanism in shaping the bivariate dependence of density on mass and Galactocentric distance for Milky Way GCs with masses 10 6 M , and it is possible, but not required, that GCs formed with similar scaling relations as ultra-compact dwarf galaxies. We use a fast cluster evolution model to fit a parameterised model for the initial properties of Milky Way GCs to the observed present-day properties. The best-fit cluster initial mass function is substantially flatter (power-law index α = −0.6 ± 0.2) than what is observed for young massive clusters (YMCs) forming in the nearby Universe (α −2). A slightly steeper CIMF is allowed when considering the metal-rich GCs separately (α −1.2 ± 0.4). If stellar mass loss and two-body relaxation in the Milky Way tidal field are the dominant disruption mechanisms, then GCs formed differently from YMCs.

Mass–radius relation of intermediate-age disc super star clusters of M82

“…The distribution at the high-mass end of the CMF falls sharply, which is found to be a common characteristic (Larsen 2009 is often fitted with a Schechter function (Schechter 1976). Clusters loose mass during their evolution, both due to stellar evolution, and dynamical processes (Gieles & Alexander 2017). The former process is not expected to alter the slope of the function, as long as the IMF of stars is independent of the mass of the clusters, whereas the impact of the latter process is mass-dependent and hence will influence the CMF of evolving clusters (Gieles 2009).…”