A new resonance-like feature in the outer disc of the Milky Way

Ronald Drimmel, Shourya Khanna, Elena D'Onghia, Thorsten Tepper-García, Joss Bland-Hawthorn, Laurent Chemin, Vincenzo Ripepi, Mercé Romero-Gómez, Pau Ramos, Eloisa Poggio, Rene Andrae, Ronny Blomme, Tristan Cantat-Gaudin, Alfred Castro-Ginard, Gisella Clementini, Francesca Fiqueras, Yves Frémat, Morgan Fouesneau, Kevin Jardin, Alex Lobel, Douglas Marshall, Tatiana Muraveva

Published 2022-07-26Version 1

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 Gaia DR3, 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 search 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.