Arnold, B, Wright, NJ and Parker, RJ (2022) Quantifying kinematic substructure in star-forming regions with statistical tests of spatial autocorrelation. Monthly Notices of the Royal Astronomical Society. ISSN 1365-2966

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We investigate whether spatial-kinematic substructure in young star-forming regions can be quantified using Moran's $I$ statistic. Its presence in young star clusters would provide an indication that the system formed from initially substructured conditions, as expected by the hierarchical model of star cluster formation, even if the cluster were spatially smooth and centrally concentrated. Its absence, on the other hand, would be evidence that star clusters form monolithically. The Moran's $I$ statistic is applied to $N$-body simulations of star clusters with different primordial spatial-velocity structures, and its evolution over time is studied. It is found that this statistic can be used to reliably quantify spatial-kinematic substructure, and can be used to provide evidence as to whether the spatial-kinematic structure of regions with ages $\lesssim$ 6 Myr is best reproduced by the hierarchical or monolithic models of star formation. Moran's $I$ statistic is also able to conclusively say whether the data are $not$ consistent with initial conditions that lack kinematic substructure, such as the monolithic model, in regions with ages up to, and potentially beyond, 10 Myrs. This can therefore provide a kinematic signature of the star cluster formation process that is observable for many Myr after any initial spatial structure has been erased.

Item Type: Article
Additional Information: © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (
Uncontrolled Keywords: methods: statistical, stars: formation, stars: kinematics and dynamics, open clusters and associations: general
Subjects: Q Science > Q Science (General)
Q Science > QB Astronomy
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Related URLs:
Depositing User: Symplectic
Date Deposited: 09 Aug 2022 08:57
Last Modified: 09 Aug 2022 08:57

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