2023/07/12 by Danial Langeroodi, J. Hjorth, Langeroodi, Danial +1
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Astronomy and Astrophysical Research
paper · pdf · doi:10.48550/arxiv.2307.06336
The empirical anti-correlation between gas-phase metallicity and star formation rate (SFR) at a fixed stellar mass, known as the fundamental metallicity relation (FMR), is commonly interpreted as an equilibrium state in the interplay between gas infall, enrichment, and gas removal. JWST/NIRSpec spectroscopy has shown a z>3 deviation from the local-universe FMR calibrations, suggesting that these galaxies are potentially caught out of equilibrium. To investigate this, we inferred the stellar population, nebular, and morphological properties of 427 galaxies at 3109M\odot galaxies exhibit negligible redshift evolution. We also confirm the redshift evolution of the FMR: z>3 galaxies appear metal-deficient compared to expectations for their stellar mass and SFR according to the local-universe FMR. This offset grows with redshift. Metal deficiency is correlated with compactness: galaxies most offset from the average mass-size relation are also the most metal-poor for their stellar mass and SFR. We interpret this as a product of bursty star formation: compact galaxies exhibit elevated SFR surface densities, indicating that they are observed during burst episodes triggered by gas infall. While accretion of metal-poor gas has reduced their gas-phase metallicity by diluting the interstellar medium, they are observed prior to chemical yield release by newly formed massive stars. Simply, they are chemically out of equilibrium compared to the equilibrium state known as the FMR.