The G-dwarf distribution in star-forming galaxies: A tug of war between infall and outflow

In the past, the cumulative metallicity distribution function (CMDF) turned out to be a useful tool to constrain the accretion history of various components of the Milky Way. In this Letter, by means of analytical, leaky-box chemical evolution models (i.e. including both infall and galactic outflows), we study the CMDF of local star-forming galaxies that follow two fundamental empirical scaling relations, namely the mass-metallicity and main sequence relations. Our analysis shows that galactic winds, which are dominant mostly in low-mass systems, play a fundamental role in shaping this function and, in particular, in determining its steepness and curvature. We show that the CMDF of low-mass (M-star/M-circle dot <= 10(9.5)) and high-mass (M-star/M-circle dot> 10(10.5)) galaxies substantially deviate from the results of a 'closed-box' model, as the evolution of the former (latter) systems is mostly dominated by outflows (infall). In the context of galactic downsizing, we show that downward-concave CMDFs (associated with systems with extremely small infall timescales and with very strong winds) are more frequent in low-mass galaxies, which include larger fractions of young systems and present more substantial deviations from equilibrium between gas accretion and reprocessing (either via star formation or winds).

Automated summary

Analyzing the CMDFs of local star-forming galaxies, we find that galactic winds play a significant role in shaping the function, with low-mass systems showing a greater impact. The CMDFs of low-mass and high-mass galaxies deviate notably from a 'closed-box' model, as the evolution of these systems is influenced by outflows and infall. Additionally, in the context of galactic downsizing, low-mass galaxies are more likely to exhibit downward-concave CMDFs, indicating larger fractions of young systems and substantial deviations from equilibrium.