Investigating the initial conditions of globular clusters via N-body simulations: I. half-mass radius and stellar density
Abstract
Born out of the turbulent, dense gas of the early Universe, globular clusters (GCs) represent a significantly different star-formation mode compared to the local Universe. To quantify the initial cluster conditions, we perform the long-term dynamical evolution of GCs using the high-precision direct N-body simulation code PeTar. As the first step in a series of studies, we investigate the two low-mass outer-halo GCs, Eridanus and Whiting 1. By comparing simulated number density profiles with observations, we derive best-fit initial half-mass radii of 2.0 ± 1.0 pc for Eridanus and 2.5 ± 0.5 pc for Whiting 1, corresponding to initial surface densities of 2592.03 M⊙ pc−2 and 226.35 M⊙ pc−2, respectively -- 2-3 orders of magnitude higher than their present-day values. The absence of multiple populations (MPs) in Whiting 1 and young massive clusters (YMCs), in contrast to the MP-hosting Eridanus, supports the scenario that MP formation requires higher initial surface density and/or lower metallicity. Using the simulations as a template, we identify five high-probability extra-tidal candidates of Whiting 1 from Gaia DR3 and APOGEE DR17, which exhibit coherent kinematics and chemical abundances. Our results demonstrate that the diffuse states of low-mass GCs are the product of long-term dynamical expansion and tidal stripping, and that their primordial configurations were significantly denser.
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BibTeX
@misc{huang2026investigating,
title = {{Investigating the initial conditions of globular clusters via $N$-body simulations: I. half-mass radius and stellar density}},
author = {Ruoyun Huang and Baitian Tang and Long Wang and Holger Baumgardt and Xia Li and Genhao Liu and Jundan Nie and Hao Tian},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.06648},
eprint = {2611.06648},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.06648},
}
RIS
TY - UNPB
TI - Investigating the initial conditions of globular clusters via N-body simulations: I. half-mass radius and stellar density
AU - Ruoyun Huang
AU - Baitian Tang
AU - Long Wang
AU - Holger Baumgardt
AU - Xia Li
AU - Genhao Liu
AU - Jundan Nie
AU - Hao Tian
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.06648
UR - https://arxiv.org/abs/2611.06648
AB - Born out of the turbulent, dense gas of the early Universe, globular clusters (GCs) represent a significantly different star-formation mode compared to the local Universe. To quantify the initial cluster conditions, we perform the long-term dynamical evolution of GCs using the high-precision direct N-body simulation code PeTar. As the first step in a series of studies, we investigate the two low-mass outer-halo GCs, Eridanus and Whiting 1. By comparing simulated number density profiles with observations, we derive best-fit initial half-mass radii of 2.0 ± 1.0 pc for Eridanus and 2.5 ± 0.5 pc for Whiting 1, corresponding to initial surface densities of 2592.03 M_⊙ pc^−2 and 226.35 M_⊙ pc^−2, respectively -- 2-3 orders of magnitude higher than their present-day values. The absence of multiple populations (MPs) in Whiting 1 and young massive clusters (YMCs), in contrast to the MP-hosting Eridanus, supports the scenario that MP formation requires higher initial surface density and/or lower metallicity. Using the simulations as a template, we identify five high-probability extra-tidal candidates of Whiting 1 from Gaia DR3 and APOGEE DR17, which exhibit coherent kinematics and chemical abundances. Our results demonstrate that the diffuse states of low-mass GCs are the product of long-term dynamical expansion and tidal stripping, and that their primordial configurations were significantly denser.
ER -