Linear gas-consumption law ($\psi =ϵM_g$)

A linear gas-consumption law assumes that the net rate of locking mass into long-lived stars is proportional to the gas mass, $\psi =ϵM_g$, with constant $ϵ$. In a leaky-box model of galactic chemical evolution with ambient-metallicity outflow $\alpha \psi$, gas mass decays as $M_g=M_{g,0}{e}^{-(1+\alpha )ϵt}$, while gas-phase metallicity grows as $Z=Z_0+pϵt$. The wind changes the time to consume gas but, under these assumptions, not the enrichment rate at a given time.