Armstrong, JJ, Wright, NJ, Jeffries, RD, Jackson, RJ and Cantat-Gaudin, T (2022) The structure and 3D kinematics of vela OB2. Monthly Notices of the Royal Astronomical Society, 517 (4). 5704 - 5720. ISSN 0035-8711

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The kinematics of stars in OB associations can provide insights into their formation, dynamical evolution, and eventual fate. The low-mass stellar content of OB associations are sufficiently numerous as to provide a detailed sampling of their kinematic properties, however spectroscopy is required to confirm the youth of individual stars and to get 3D kinematics. In this paper, we present and analyse results from a large spectroscopic survey of Vela OB2 conducted using 2dF/HERMES on the AAT. This spectroscopy is used to confirm the youth of candidate young stars and determine radial velocities, which are combined with proper motions and parallaxes from Gaia to measure 3D positions and velocities. We identify multiple separate kinematic groups in the region, for which we measure velocity dispersions and infer their virial states. We measure expansion rates for all these groups and find strong evidence for anisotropic expansion in the Vela OB2 association of at least 11σ significance in all three dimensions, as well as some evidence for expansion in the γ Vel and P Puppis clusters. We trace back the motions of these groups into the past and find that the open cluster NGC 2547 is an interloper in the Vela OB2 region and actually formed >100 pc away from the association. We conclude that Vela OB2 must have formed with considerable spatial and kinematic substructure over a time-scale of ∼10 Myr, with clear temporal substructure within the association, but no clear evidence for an age gradient.

Item Type: Article
Additional Information: © 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Uncontrolled Keywords: techniques: spectroscopic; surveys; stars: kinematics and dynamics; stars: pre-main-sequence; open clusters and associations: individual: Vela OB2, NGC 2547, gamma, Vel, P Puppis
Subjects: Q Science > Q Science (General)
Q Science > QB Astronomy
Q Science > QB Astronomy > QB460 Astrophysics
Q Science > QB Astronomy > QB600 Planets. Planetology
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Depositing User: Symplectic
Date Deposited: 30 Nov 2022 08:49
Last Modified: 21 Feb 2023 09:13

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