Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VII. Energy Equipartition
Laura L. Watkins (1,2,3), Roeland P. van der Marel (4,5), Mattia, Libralato (1), Andrea Bellini (4), Jay Anderson (4), Mayte Alfaro-Cuello (4), ((1) ESA-AURA STScI, (2) ESO, (3) Vienna, (4) STScI, (5) JHU)

TL;DR
This study measures the degree of energy equipartition in nine Galactic globular clusters using Hubble Space Telescope proper motions, finding partial equipartition correlated with relaxation times and no significant radial variation.
Contribution
It provides the first energy equipartition analysis for most of these clusters and introduces a large, cleaned dataset for future dynamical studies.
Findings
All clusters show partial, not full, energy equipartition.
The degree of equipartition correlates with relaxation times.
No significant radial trend in equipartition was observed.
Abstract
We examine the degree of energy equipartition in 9 Galactic globular clusters using proper motions measured with the Hubble Space Telescope. For most clusters in the sample, this is the first energy equipartition study ever performed. This study is also the largest of its kind, albeit with only 9 clusters. We begin by rigorously cleaning the catalogues to remove poor-quality measurements and to ensure high signal-to-noise for the study. Using the cleaned catalogues, we investigate how velocity dispersion changes with stellar mass . We fit two functional forms: the first, a classic power-law of the form where is the degree of energy equipartition, and the second from Bianchini et al. (2016) parameterised by an equipartition mass where changes with stellar mass. We find that both functions fit well but cannot distinguish with…
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