On bursty star formation during cosmological reionization — influence on the metal and dust content of low-mass galaxies

Abstract Observations indicate that high-redshift galaxies undergo episodic star formation bursts, driving strong outflows that expel gas and suppress accretion. We investigate the consequences for metal and dust content of galaxies at z ≥ 5 using our semi-analytical model, A SHVINI . We track gas-phase and stellar metallicities ( Z g, Z ⋆) and dust mass ( M d ) in dark matter haloes spanning M h = 10 6 -10 11 M ⊙ , comparing continuous and bursty star formation scenarios- which reflect underlying assumptions of instantaneous and delayed feedback - and we allow for metallicity-dependent feedback efficiency. Delayed feedback induces oscillations in Z g and Z ⋆ , with Z g declining sharply at low stellar and halo masses; the mass scale of this decline increases toward lower redshift. Reionization introduces significant scatter in Z g , producing an upturn followed by rapid decline. Metallicity-dependent feedback moderates this decline at z = 7-10, flattening the Z g –mass relation to ≃ 0.03–0.04Z ⊙ . Dust production tracks Z g but is sensitive to burst history, causing delayed enrichment. Our results show that burst-driven feedback decouples Z g and Z ⋆ , imprints intrinsic scatter in mass–metallicity relations, and delays dust growth. These effects are strongest in low-mass halos ( M h ∼ 10 7 M ⊙ ), where shallow potentials amplify the impact of feedback. Our results are consistent with recent hydrodynamical and semi-analytical simulations and provide context for interpreting JWST ( James Webb Space Telescope ) metallicity and dust measurements, highlighting the importance of episodic star formation in early galaxy chemical evolution.