Introducing the Rhea simulations of Milky Way-like galaxies

I. Effect of gravitational potential on morphology and star formation

¹ Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
² Centre de Recherche Astrophysique de Lyon UMR5574, ENS de Lyon, Univ. Lyon1, CNRS, Université de Lyon, 69007 Lyon, France
³ École Polytechnique Fédérale de Lausanne, Observatoire de Sauverny, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁴ Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer Feld 225, 69120 Heidelberg, Germany
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁶ Elizabeth S. and Richard M. Cashin Fellow at the Radcliffe Institute for Advanced Studies at Harvard University, 10 Garden Street, Cambridge, MA 02138, USA
⁷ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁸ Istituto di Astrofisica e Planetologia Spaziali (IAPS), INAF, Via Fosso del Cavaliere 100, 00133 Roma, Italy
⁹ SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
¹⁰ Como Lake centre for Astrophysics (CLAP), DiSAT, Universitá degli Studi dell’Insubria, Dipartimento di Scienza e Alta Tecnologia, Via Valleggio 11, 22100 Como, Italy
¹¹ Alma Mater Studiorum Università di Bologna, Dipartimento di Fisica e Astronomia (DIFA), Via Gobetti 93/2, 40129 Bologna, Italy
¹² INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

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Received: 12 September 2024
Accepted: 24 August 2025

Abstract

The Milky Way is a complex ecosystem. We can obtain detailed observations of it by probing the physical mechanisms that determine its interstellar medium. For a detailed comparison with observations and to provide theories for missing observables, the Milky Way must be modelled as accurately as possible. However, details of the Galactic structure are not fully defined by observations, which raises the need for more generalised models. With the Rhea simulations, we present a set of Milky Way-like simulations containing detailed physics of the interstellar medium as well as star formation and stellar feedback. We conducted two simulations that differ in the gravitational potential: one fitted to several structural details derived from observations and another that only reproduces the most basic quantities. We find little difference in the overall morphology except for the bar region, which funnels gas towards the Galactic inner region and therefore prevents quenching in the centre. Despite differences with galacto-centric radius, the global star formation rate is almost identical in both setups. A spiral arm potential does not influence properties of groups of formed stars. A bar potential, however, reduces the size and formation time of those associations. We conclude that a spiral arm potential has little influence on star formation in the Galaxy, except for producing long-lived spiral structures instead of transient ones, and that a galactic bar potential has a noticeable influence on star formation, mainly within the innermost 2.5 kpc.