A JWST project on 47 Tucanae: Kinematics, energy equipartition, and anisotropy of multiple populations

¹ Dipartimento di Fisica e Astronomia Galileo Galilei, Univ. di Padova, Vicolo dell’Osservatorio 3, Padova 35122, Italy
² Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, Padova 35122, Italy
³ Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia
⁴ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
⁵ Department of Astronomy, Indiana University, Bloomington, IN 47401, USA
⁶ Department of Physics and Astronomy, Sejong University, 209 Neungdong-ro, Gwangjin-Gu, Seoul 05006, Republic of Korea
⁷ Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218, USA
⁸ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
⁹ South-Western Institute for Astronomy Research, Yunnan University, Kunming 650500, PR China
¹⁰ Universidade Federal do Rio Grande do Sul, Instituto de Física, Av. Bento Gonçalves 9500, Porto Alegre, RS, Brazil

^★ Corresponding author: tuila.ziliotto@unipd.it

Received: 5 February 2025
Accepted: 25 April 2025

Abstract

Recent work with JWST has demonstrated its capability to identify and chemically characterize multiple populations in globular clusters down to the H-burning limit. In this study, we explore the kinematics of multiple populations in the globular cluster 47 Tucanae by combining data from JWST, HST, Gaia, and ground-based telescopes. We analyzed velocity dispersion and anisotropy profiles from the cluster center out to ∼10R_h. Our findings indicate that while first population (1G) stars’ motions are isotropic, second population (2G) stars’ motions are significantly radially anisotropic. These results align with the predictions of simulations of the dynamical evolution of clusters where 2G stars are initially more centrally concentrated than 1G stars. Furthermore, we subdivided the 2G population into two subpopulations: 2G_A and 2G_B, with the latter being more chemically extreme. We compared their dynamical profiles and found no significant differences. For the first time, we measured the degree of energy equipartition among the multiple populations of 47 Tucanae. Overall, within the analyzed radial range (∼2–4R_h), both populations exhibit a low degree of energy equipartition. The most significant differences between 1G and 2G stars are observed in the tangential velocity component, where 2G stars are characterized by a stronger degree of energy equipartition than 1G stars. In the radial component, the behavior of 1G and 2G stars is more variable, with differences largely dependent on radius. Moreover, our analysis reveals that the ratio of rotational velocity to velocity dispersion is larger for the 2G population. Finally, we found that 1G stars exhibit a higher skewness in their tangential proper motions than 2G stars, providing additional evidence of kinematic differences between the two stellar generations.