A new resonance-like feature in the outer disc of the Milky Way
R. Drimmel, S. Khanna, Elena D’Onghia, Thor Tepper-García, Joss Bland‐Hawthorn, L. Chemin, V. Ripepi, M. Romero-Gómez, P. Ramos, E. Poggio, R. Andrae, R. Blomme, T. Cantat-Gaudin, A. Castro-Ginard, G. Clementini, F. Figueras, M. Fouesneau, Y. Frémat, A. Lobel, D. J. Marshall, T. Muraveva
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.