Gravitational wave (GW) astronomy has revolutionized our view of the Universe by providing direct evidence of the coalescence of compact-object binaries, such as black holes and neutron stars. Since the first detection in 2015, over 90 GW events have been recorded, yet the astrophysical origin of these sources remains unclear. This fundamental uncertainty hampers our ability to interpret the observed population and forecast the discoveries expected from next-generation detectors like the Einstein Telescope and LISA.
Current models suggest two broad pathways for binary formation: isolated evolution of stellar pairs and dynamical assembly in dense stellar environments. However, both fail to fully explain the observed properties of GW sources, such as their masses, spins, and eccentricities. This has highlighted the need to explore alternative environments, particularly galactic nuclei — regions hosting supermassive black holes surrounded by dense stellar populations and, in some cases, gas disks associated with active galactic nuclei (AGNs). These extreme environments can facilitate the formation and merger of compact-object binaries through mechanisms such as gravitational perturbations, gas drag, and multi-body interactions.
The GWnucleus project addresses this gap by systematically investigating the role of galactic nuclei in shaping GW sources. The project develops a new generation of computational models that combine high-precision N-body dynamics with fast Monte Carlo simulations, tailored to account for the complex physics of dense stellar environments and AGN disks. By simulating millions of binary systems across a wide range of conditions, GWnucleus will build mock catalogs of GW sources that can be directly compared with real observations.
The project is structured around three main objectives. First, it quantifies how gravitational perturbations from the central black hole and surrounding stars influence binary evolution. Second, it models the effects of gas physics in AGN disks, such as migration and disk-induced torques. Third, it connects these theoretical models with current GW observations through population synthesis and Bayesian inference, providing a framework to assess the likelihood that a given observed GW event originated in a galactic nucleus.
The expected impact of GWnucleus is significant. It will deliver an open-source simulation framework and public data products, enabling researchers to explore a new formation channel for GW sources. This contributes directly to the goals of the European Research Area in fostering open science, interdisciplinary collaboration, and data-driven discovery. By improving our understanding of compact-object mergers, GWnucleus also supports broader astrophysical questions, including galaxy evolution, stellar dynamics, and the formation of supermassive black holes.
In a broader context, the project aligns with strategic European priorities in space science and research infrastructures, complementing the scientific missions of upcoming observatories. It also contributes to public engagement through scientific outreach, visualizations, and open-access dissemination of results. By combining innovative computational techniques with pressing scientific questions, GWnucleus stands at the frontier of gravitational-wave astrophysics and aims to transform our understanding of where and how the most extreme objects in the Universe are born.
