The following material is a supplement to my Cool Stars 18 poster presentation.
Animated versions of the UVW and XYZ plots can be found here
Animated versions of the UVW and XYZ plots can be found here
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The plots show 1000 Monte Carlo trials per bona-fide member, each run back into the past using an epicyclic approximation to the Galactic gravitational potential. At each timestep, the position and extent of the cluster is determined, and the separations between all of the stars and the cluster center is shown here.
The above tracebacks of beta Pictoris, TW Hydra, Tucana-Horologium, and AB Doradus demonstrate the current problem: If you take the best available data for the bona-fide members of the nearby young moving groups (here, represented by the lists that appeared in Gagne et al. (2014) with minor modifications to represent only the primaries of the star systems) the stars do not trace back to the same spatial locations as each other, with the possible exception of TW Hydra, aged 5-15 Myr.
The above tracebacks of beta Pictoris, TW Hydra, Tucana-Horologium, and AB Doradus demonstrate the current problem: If you take the best available data for the bona-fide members of the nearby young moving groups (here, represented by the lists that appeared in Gagne et al. (2014) with minor modifications to represent only the primaries of the star systems) the stars do not trace back to the same spatial locations as each other, with the possible exception of TW Hydra, aged 5-15 Myr.
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The plots above compare the position of the brown dwarf 2M0608-2753 (the 1-sigma, 2-sigma, and 3-sigma uncertainty envelopes are shown in increasingly light shades of gray), believed by Rice et al. (2010) to be a member of beta Pictoris. The spatial extend of the cluster (and its 1-sigma error) is shown in red; a true member should be closer to the center than that, at the time of formation. The plots above demonstrate that unless beta Pictoris is 10-12 Myr old (which is no longer believed), the system is not a good member of any of the above four groups, although it does fit beta Pictoris the best. The supposition here is that our data are not sufficiently precise.