2016/05/31 by Mark Gieles, Florent Renaud · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/mnrasl/slw163
published as Mon. Not. R. Astron. Soc. 463, L103-L107 (2016) · 5 pages, 3 figures, updated to match journal style
arxiv created 2016/09/16 · arxiv updated 2016/09/19
The radii of young (<100 Myr) star clusters correlate only weakly with their masses. This shallow relation has been used to argue that impulsive tidal perturbations, or `shocks', by passing giant molecular clouds (GMCs) preferentially disrupt low-mass clusters. We show that this mass-radius relation is in fact the result of the combined effect of two-body relaxation and repeated tidal shocks. Clusters in a broad range of environments including those like the solar neighbourhood evolve towards a typical radius of a few parsecs, as observed, independent of the initial radius. This equilibrium mass-radius relation is the result of a competition between expansion by relaxation and shrinking due to shocks. Interactions with GMCs are more disruptive for low-mass clusters, which helps to evolve the globular cluster mass function (GCMF). However, the properties of the interstellar medium in high-redshift galaxies required to establish a universal GCMF shape are more extreme than previously derived, challenging the idea that all GCs formed with the same power-law mass function.