Wright, NJ and Mamajek, EE (2018) The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1. Monthly Notices of the Royal Astronomical Society, 476 (1). pp. 381-398. ISSN 1365-2966

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We present a kinematic study of the Scorpius-Centaurus (Sco-Cen) OB association (Sco OB2) using Gaia DR1 parallaxes and proper motions. Our goal is to test the classical theory that OB associations are the expanded remnants of dense and compact star clusters disrupted by processes such as residual gas expulsion. Gaia astrometry is available for 258 out of 433 members of the association, with revised Hipparcos astrometry used for the remainder. We use this data to confirm that the three subgroups of Sco-Cen are gravitationally unbound and have non-isotropic velocity dispersions, suggesting they have not had time to dynamically relax. We also explore the internal kinematics of the subgroups to search for evidence of expansion. We test Blaauw’s classical linear model of expansion, search for velocity trends along the Galactic axes, compare the expanding and non-expanding convergence points, perform traceback analysis assuming both linear trajectories and using an epicycle approximation, and assess the evidence for expansion in proper motions corrected for virtual expansion / contraction. None of these methods provide coherent evidence for expansion of the subgroups, with no evidence to suggest that the subgroups had a more compact configuration in the past. We find evidence for kinematic substructure within the subgroups that supports the view that they were not formed by the disruption of individual star clusters. We conclude that Sco-Cen was likely born highly substructured, with multiple small-scale star formation events contributing to the overall OB association, and not as single, monolithic bursts of clustered star formation.

Item Type: Article
Additional Information: This is the accepted author manuscript (AAM). The final published version (version of record) is available online via Oxford University Press at https://doi.org/10.1093/mnras/sty207 - please refer to any applicable terms of use of the publisher.
Uncontrolled Keywords: stars, formation, kinematics and dynamics, open clusters and associations, individual, Scorpius-Centaurus, Sco OB2, Upper Scorpius, Upper Centaurus-Lupus, Lower Centaurus-Crux
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Depositing User: Symplectic
Date Deposited: 08 Feb 2018 09:49
Last Modified: 02 May 2018 08:24
URI: https://eprints.keele.ac.uk/id/eprint/4433

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