Stacey, H.R.Kaasinen, M.O’Riordan, C.M.McKean, J.P.Powell, D.M.Rizzo, F.2025-11-182025-11-182025-01Stacey, H.R., Kaasinen, M., O'Riordan, C.M. et al. 2025, 'A nuclear spiral in a dusty star-forming galaxy at z = 2:78', Astronomy & Astrophysics, vol. 693, art. L17, pp. 1-5. https://doi.org/10.1051/0004-6361/202452518.0004-6361 (print)1432-0746 (online)10.1051/0004-6361/202452518http://hdl.handle.net/2263/105321The nuclear structure of dusty star-forming galaxies is largely unexplored but harbours critical information about their structural evolution. Here, we present long-baseline Atacama Large (sub-)Millimetre Array (ALMA) continuum observations of a gravitationally lensed dusty star-forming galaxy at z = 2.78. We use a pixellated lens modelling analysis to reconstruct the rest-frame 230 μm dust emission with a mean resolution of ≈55 pc and demonstrate that the inferred source properties are robust to changes in lens modelling methodology. The central 1 kpc is characterised by an exponential profile, a dual spiral arm morphology and an apparent super-Eddington compact central starburst. We find tentative evidence for a nuclear bar in the central 300 pc. These features may indicate that secular dynamical processes play a role in accumulating a high concentration of cold gas that fuels the rapid formation of a compact stellar spheroid and black hole accretion. We propose that the high spatial resolution provided by long-baseline ALMA observations and strong gravitational lensing will give key insights into the formation mechanisms of massive galaxies.en© The Authors 2025. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0).Gravitational lensing: strongGalaxies: evolutionGalaxies: formationGalaxies: high-redshiftGalaxies: structureSubmillimeter: galaxiesArticle