| Abstract: |
The evolution of galaxies is regulated by dynamical processes such as gas inflow and outflow. These processes are difficult to observe directly, but they leave a distinct imprint on the chemical content of galaxies. The regularity of galaxy evolution is reflected in scaling relations involving gas metallicity, such as the mass–metallicity relation (MZR) and the fundamental metallicity relation (FMR), and their evolution across cosmic time. Despite decades of observational effort pushing these relations to the low-mass and high-redshift regimes, we still lack a unified framework to understand them. In this talk, I will present a unified picture for these scaling relations and their redshift evolution, starting from two mass-continuity equations. I will show that the FMR is not a consequence of galaxies being in equilibrium; instead, it spans galaxies from the inflow-driven regime to equilibrium, and its redshift invariance encodes how the star formation efficiency and mass-loading factor depend on stellar mass and redshift. Time permitting, I will also revisit several classic works relating gas metallicity to gas flows, and show how they fit within our framework.
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