2025A&A...701A...2K

Context. The cosmic time evolution of the radial structure is one of the key topics in the investigation of disc galaxies. In the build-up of galactic discs, gas infall is an important ingredient and it produces radial gas inflows as a physical consequence of angular momentum conservation since the infalling gas onto the disc at a specific radius has lower angular momentum than the circular motions of the gas at the point of impact. NGC 300 is a well-studied isolated, bulgeless, and low-mass disc galaxy ideally suited for an investigation of galaxy evolution with radial gas inflows.
Aims. Our aim is to investigate the effects of radial gas inflows on the physical properties of NGC 300, for example the radial profiles of HI gas mass and star formation rate (SFR) surface densities, specific star formation rate (sSFR), and metallicity, and to study how the metallicity gradient evolves with cosmic time.
Methods. A chemical evolution model for NGC 300 was constructed by assuming its disc builds up progressively by the infalling of metal-poor gas and the outflowing of metal-enriched gas. Radial gas inflows were also considered in the model. We used the model to build a bridge between the available data (e.g. gas content, SFR, and chemical abundances) observed today and the galactic key physical processes.
Results. Our model including the radial gas inflows and an inside-out disc formation scenario can simultaneously reproduce the present-day observed radial profiles of HI gas mass surface density, SFR surface density, sSFR, gas-phase, and stellar metallicity. We find that, although the value of radial gas inflow velocity is as low as -0.1 km s^–1, the radial gas inflows steepen the present-day radial profiles of HI gas mass surface density, SFR surface density, and metallicity, but flatten the radial sSFR profile. Incorporating radial gas inflows significantly improves the agreement between our model predicted present-day sSFR profile and the observations of NGC 300. Our model predictions are also in good agreement with the star-forming galaxy main sequence and the mass-metallicity relation of star-forming galaxies. It predicts a significant flattening of the metallicity gradient with cosmic time. We also find that the model predicted star formation has been more active recently, indicating that the radial gas inflows may help to sustain star formation in local spirals, at least in NGC 300.