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arXiv · 2607.19717

When Galaxies Refuel: Evolution of the Perturbed Spiral Galaxy NGC1385

Xiaoyu Kang·Eva Sextl·Rolf-Peter Kudritzki·Hassen M. Yesuf·Fenghui Zhang·Ruixiang Chang·Xiejin Li·Yunkun Han
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Abstract

The spiral galaxy NGC 1385 is characterized by a vigorous and protracted history of star formation, particularly in its central regions, leading to a current star formation rate that surpasses those of comparable systems. We analyze the evolution history of the galaxy using spatially resolved optical and submillimeter spectroscopy obtained from the PHANGS survey combined with WALLABY radio survey data. We construct radial distributions of star formation rate and the interstellar medium (ISM) neutral and molecular gas mass surface densities and measure the metallicity distribution of the stellar populations using a refined full-spectral fitting population synthesis method together with a determination of ISM oxygen abundances using H\,II region emission lines. The metallicities of the young stars and the ISM are similar and show an almost flat distribution. This is crucially different from previous work which had found a positive gradient for the average metallicities of the stars. We fit a chemical evolution model (incorporating gas infall, outflow, and radial inflow) to the observed data of NGC\,1385. Based on this fit, the evolution of NGC\,1385 is characterized by the typical inside-out disk formation of spiral galaxies -- even though our model does not assume an a priori shorter gas infall timescale for the inner disk than for the outer disk. However, the galaxy has experienced sustained star formation over gigayear timescales with a star formation efficiency a factor of two higher than normal. This explains the high metallicity of the young stars of 0.15 to 0.2\,dex higher than solar and the flat distribution of metallicity across the disk. The model predictions for the metallicities of the stars align well with the observed values, supporting the robustness of both our refined spectral fitting analysis and the inferred evolutionary scenario.

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Xiaoyu Kang, Eva Sextl, Rolf-Peter Kudritzki, Hassen M. Yesuf, Fenghui Zhang, Ruixiang Chang, Xiejin Li, Yunkun Han. 2026-08-04. When Galaxies Refuel: Evolution of the Perturbed Spiral Galaxy NGC1385. https://arxiv.org/abs/2607.19717

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