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Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2

Wright

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Abstract

For the first time, we have explored the spatial substructure of the Cygnus OB2 association using parallaxes from the recent second Gaia data release. We find significant line-of-sight substructure within the association, which we quantify using a parametrized model that reproduces the observed parallax distribution. This inference approach is necessary due to the non-linearity of the parallax distance transformation and the asymmetry of the resulting probability distribution. Using a Markov Chain Monte Carlo ensemble sampler and an unbinned maximum likelihood test, we identify two different stellar groups superposed on the association. We find the main Cygnus OB2 group at ~1760 pc, further away than recent estimates have envisaged, and a foreground group at ~1350 pc. We also calculate individual membership probabilities and identify outliers as possible non-members of the association.

Acceptance Date Jan 9, 2019
Publication Date Apr 1, 2019
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Pages 1838 -1842
DOI https://doi.org/10.1093/mnras/stz117
Keywords astrometry, parallaxes, stars: distances, stars: early-type, stars: massive, open clusters and associations: individual: Cygnus OB2
Publisher URL https://doi.org/10.1093/mnras/stz117

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