Chemical evolution in nuclear stellar discs

¹ Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, The Netherlands
² Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK

^★ Corresponding authors: friske@astro.rug.nl; r.schoenrich@ucl.ac.uk

Received: 1 April 2025
Accepted: 20 June 2025

Abstract

Context. Nuclear stellar discs (NSDs) have been observed in the vast majority of barred disc galaxies, including the Milky Way. Their intense star formation is sustained by the intense gas inflows driven by their surrounding bars and frequently supports a large-scale galactic fountain. Despite their central role in galaxy evolution, their chemical evolution remains largely unexplored.

Aims. We argue that the chemical composition of NSDs is best understood relative to the bar tips from which their gas is drawn. We make predictions of the detailed abundance profiles of gas and young stars within the NSD under different accretion scenarios from the galactic bar.

Methods. We present the first systematic, multi-zonal modelling of the chemical evolution of nuclear stellar discs based on the RAMICES II code.

Results. We show that due to their different star formation history to galactic discs, NSDs offer a unique laboratory in which to break parameter degeneracies in chemical evolution models. This allows us to identify the effects of the main parameters guiding NSD nucleosynthesis and disentangle them from the global enrichment history. We also show how the mode of gas accretion onto the NSD imprints on the gas abundance profiles for two edge cases and make predictions that can be tested with observations.