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

TL;DR

This paper uses analytical models to study how infall and outflows shape the metallicity distribution in star-forming galaxies, revealing mass-dependent effects and the importance of winds in low-mass systems.

Contribution

It introduces a chemical evolution model incorporating both infall and outflows to explain the metallicity distribution functions in galaxies of different masses.

Findings

Galactic winds significantly influence the shape of the CMDF.

Low-mass galaxies show steep, downward-concave CMDFs due to strong winds.

High-mass galaxies' CMDFs are dominated by infall processes.

Abstract

In the past, the cumulative metallicity distribution function (CMDF) turned out as 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$_{\odot} \le 10^{9.5}$) and high-mass (M$_{\star}$/M$_{\odot}$>10$^{10.5}$) galaxies deviate substantially 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).