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

¹ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, TO, Italy
e-mail: ronald.drimmel@inaf.it
² Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA
³ Sydney Institute for Astronomy, School of Physics, University of Sydney, Physics Rd, Camperdown, Sydney, NSW 2006, Australia
⁴ Centre of Excellence for All Sky Astrophysics in Three Dimensions (ASTRO-3D), Stromlo, ACT 2611, Australia
⁵ Centro de Astronomía – CITEVA, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile
⁶ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
⁷ Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
⁸ Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona (UB), C Martí i Franquès, 1, 08028 Barcelona, Spain
⁹ Institut d’Estudis Espacials de Catalunya (IEEC), C Gran Capità, 2-4, 08034 Barcelona, Spain
¹⁰ National Astronomical Observatory of Japan, 2 Chome-21-1 Osawa, Mitaka-shi, Tokyo 181-8588, Japan
¹¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
¹² Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹³ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
¹⁴ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
¹⁵ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
¹⁶ IRAP, Université de Toulouse, CNRS, UPS, CNES, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France

Received: 26 July 2022
Accepted: 22 November 2022

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.