Kinematic fingerprint of core-collapsed globular clusters

Abstract

Dynamical evolution drives globular clusters toward core collapse, which strongly shapes their internal properties. Diagnostics of core collapse have so far been based on photometry only, namely on the study of the concentration of the density profiles. Here we present a new method to robustly identify core-collapsed clusters based on the study of their stellar kinematics. We introduce the \textit{kinematic concentration} parameter, $c_k$, the ratio between the global and local degree of energy equipartition reached by a cluster, and show through extensive direct $N$-body simulations that clusters approaching core collapse and in the post-core collapse phase are strictly characterized by $c_k>1$. The kinematic concentration provides a suitable diagnostic to identify core-collapsed clusters, independent from any other previous methods based on photometry. We also explore the effects of incomplete radial and stellar mass coverage on the calculation of $c_k$ and find that our method can be applied to state-of-art kinematic datasets.

Accepted for publication in MNRAS Letter

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• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIV. Differences in internal kinematics of multiple stellar populations
• Structure and Internal Kinematics of Nine Inner Milky Way Globular Clusters
• Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VII. Energy Equipartition
• Early dynamics and violent relaxation of multi-mass rotating star clusters
• The Structural and Kinematic Evolution of Central Star Clusters in Dwarf Galaxies and Their Dependence on Dark Matter Halo Profiles
• Energy equipartition in multiple-population globular clusters
• A Photometric in-depth look at the core-collapsed globular cluster NGC 6284
• Searching for new observational signatures of the dynamical evolution of star clusters
• New parameters for star cluster dynamics: the effect of primordial binaries and dark remnants
• A JWST project on 47 Tucanae: kinematics, energy equipartition and anisotropy of multiple populations
• Searching for exotic object companions in the dense core of NGC 362: a multi-wavelength and multi-epoch photometric analysis
• The internal kinematics of NGC 2808 and its multiple populations
• Influences of dynamical disruptions on the evolution of pulsars in globular clusters
• Energy equipartition in Globular Clusters through the eyes of dynamical models
• Predicting Images for the Dynamics Of stellar Clusters (π-DOC): a deep learning framework to predict mass, distance and age of globular clusters
• Evolution towards energy equipartition in star clusters: effects of the tidal field, primordial binaries, and internal velocity anisotropy