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.
@article{arxiv.1901.02959,
title = {Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2},
author = {S. R. Berlanas and N. Wright and A. Herrero and J. E. Drew and D. J. Lennon},
journal= {arXiv preprint arXiv:1901.02959},
year = {2019}
}
Comments
6 pages, 3 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal