Tepper-García, ThorBland-Hawthorn, JossVasiliev, EugeneAgertz, OscarTeyssier, RomainFederrath, Christoph2025-05-232025-05-230035-8711ORCID:/0000-0002-0706-2306/work/184104792http://www.scopus.com/inward/record.url?scp=85208254822&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733751518Motivated by the need for realistic, dynamically self-consistent, evolving galaxy models that avoid the complexity of full, and zoom-in, cosmological simulations, we have developed Nexus, an integral framework to create and evolve synthetic galaxies made of collisionless and gaseous components. Nexus leverages the power of publicly available, tried-and-tested packages: the stellar-dynamics, action-based library Action-based Galaxy Modelling Architecture (AGAMA); and the adaptive mesh refinement, N-body/hydrodynamical code Ramses, modified to meet our needs. In addition, we make use of a proprietary module to account for galaxy formation physics, including gas cooling and heating, star formation, stellar feedback, and chemical enrichment. Nexus' basic functionality consists in the generation of bespoke initial conditions (ICs) for a diversity of galaxy models, which are advanced in time to simulate the galaxy's evolution. The fully self-consistent ICs are generated with a distribution-function-based approach, as implemented in the galaxy modelling module of AGAMA - up to now restricted to collisionless components, extended in this work to treat two types of gaseous configurations: hot haloes and gas discs. Nexus allows constructing equilibrium models with disc gas fractions, appropriate to model both low- and high-redshift galaxies. Similarly, the framework is ideally suited to the study of galactic ecology, i.e. the dynamical interplay between stars and gas over billions of years. As a validation and illustration of our framework, we reproduce several isolated galaxy model setups reported in earlier studies, and present a new, 'nested bar' galaxy simulation. Future upgrades of Nexus will include magnetohydrodynamics and highly energetic particle ('cosmic ray') heating.TTG acknowledges partial financial support from the Australian Research Council (ARC) through an Australian Laureate Fellowship awarded to JBH. EV acknowledges support from an STFC Ernest Rutherford fellowship (ST/X004066/1). OA acknowledges support from the Knut and Alice Wallenberg Foundation, the Swedish Research Council (grant 2019-04659), and the Swedish National Space Agency (SNSA Dnr 2023-00164). CF acknowledges funding provided by the Australian Research Council (Discovery Project DP230102280), and the Australia-Germany Joint Research Cooperation Scheme (UA-DAAD). We further acknowledge high-performance computing resources provided by the Australian National Computational Infrastructure (grants ca64, ek9) and the Pawsey Supercomputing Centre (project pawsey0810) in the framework of the National Computational Merit Allocation Scheme and the ANU Merit Allocation Scheme, by the Leibniz Rechenzentrum and by the Gauss Centre for Supercomputing (grants pr32lo, pr48pi and GCS Large-scale project 10391). TTG acknowledges partial financial support from the Australian Research Council (ARC) through an Australian Laureate Fellow- ship awarded to JBH. EV acknowledges support from an STFC Ernest Rutherford fellowship (ST/X004066/1). OA acknowledges support from the Knut and Alice Wallenberg Foundation, the Swedish Research Council (grant 2019-04659), and the Swedish National Space Agency (SNSA Dnr 2023-00164). CF acknowledges funding provided by the Australian Research Council (Discovery Project DP230102280), and the Australia-Germany Joint Research Cooperation Scheme (U A-D AAD). We further acknowledge high- performance computing resources provided by the Australian Na- tional Computational Infrastructure (grants ca64, ek9) and the Pawse y Supercomputing Centre (project pa wse y0810) in the frame- work of the National Computational Merit Allocation Scheme and the ANU Merit Allocation Scheme, by the Leibniz Rechenzentrum and by the Gauss Centre for Supercomputing (grants pr32lo, pr48pi and GCS Large-scale project 10391). Last, we are indebted to an insightful referee for a fair assessment of our work, which helped impro v e its o v erall presentation. All figures and movie frames created with MATPLOTLIB (Hunter 2007 ). All animations assembled with FFMPEG. 24 This research has made use of NASA s Astrophysics Data System (ADS) Bibliographic Services.20enPublisher Copyright: © 2024 The Author(s).hydrodynamicsmethods: analyticalmethods: numericalsoftware: simulationsstars: kinematics and dynamics2024-11-0110.1093/mnras/stae237285208254822