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

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 $z\geq\!5$ using our semi-analytical model, ASHVINI. We track gas-phase and stellar metallicities $(Z_\text{g}, Z_\star)$ and dust mass $(M_{\rm d})$ in dark matter haloes spanning $M_{\rm h} = 10^6 - 10^{11}\,M_\odot$, 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 $Z_{\rm g}$ and $Z_\star$, with $Z_{\rm g}$ declining sharply at low stellar and halo masses. This decline shifts to higher stellar and halo masses as the redshift decreases. Reionization introduces significant scatter, producing an upturn followed by rapid $Z_{\rm g}$ decline. Metallicity-dependent feedback moderates this decline at $z=7-10$, flattening the $Z_{\rm g}$-mass relation to $\simeq 0.03 - 0.04\,Z_\odot$. Dust production tracks $Z_{\rm g}$ but is sensitive to burst history, causing delayed enrichment. Our results show that burst-driven feedback decouples $Z_{\rm g}$ and $Z_\star$, imprints intrinsic scatter in mass-metallicity relations, and delays dust growth. These effects are strongest in low-mass halos $(M_{\rm h}\sim 10^7\,M_\odot)$, where shallow potentials amplify the impact of feedback. Our results are consistent with recent hydrodynamical and semi-analytical simulations and provides context for interpreting JWST metallicity and dust measurements, highlighting the importance of episodic star formation in early galaxy chemical evolution.