A new resonance-like feature in the outer disc of the Milky Way
Fouesneau, M.; Andrae, R.; Castro-Ginard, A.; Cantat-Gaudin, T.; Figueras, F.; Clementini, G.; Ripepi, V.; Drimmel, R.; Frémat, Y.; Blomme, R.; Chemin, L.; Khanna, S.; Lobel, A.; Muraveva, T.; Poggio, E.; Ramos, P.; Romero-Gómez, M.; Bland-Hawthorn, J.; D'Onghia, E.; Marshall, D.; Tepper-García, T.
Italy, United States, Australia, Chile, Spain, Japan, France, Germany, Belgium, Netherlands
Abstract
Modern astrometric and spectroscopic surveys have revealed a wealth of structure in the phase space of stars in the Milky Way, with evidence of resonance features and non-equilibrium processes. Using the third Gaia data release, we present evidence of a new resonance-like feature in the outer disc of the Milky Way. The feature is most evident in the angular momentum distribution of the young classical Cepheids, a population for which we can derive accurate distances over much of the Galactic disc. We then searched for similar features in the outer disc using a much larger sample of red giant stars, as well as a compiled list of over 31 million stars with spectroscopic line-of-sight velocity measurements. While much less evident in these two older samples, the distribution of stars in action-configuration space suggests that resonance features are present here as well. The position of the feature in action-configuration space suggests that the new feature may be related to the Galactic bar, but other possibilities are discussed.