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arXiv · 1901.02959

Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2

S. R. Berlanas·N. Wright·A. Herrero·J. E. Drew·D. J. Lennon
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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 parameterised 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. By 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.

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S. R. Berlanas, N. Wright, A. Herrero, J. E. Drew, D. J. Lennon. 2019-01-09. Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2. https://doi.org/10.1093/mnras%2Fstz117

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