Intermittent Self-Sustaining Star Formation in Low-Redshift Galaxies Exhibiting a Peak Metallicity Plateau

TL;DR

This paper proposes a model where high-mass low-redshift galaxies sustain intermittent star formation through internal gas recycling, explaining the observed metallicity plateau and star formation rates without external gas infall.

Contribution

It introduces a quantitative model for intermittent star formation in massive galaxies driven by internal gas recycling, accounting for the metallicity plateau and observed star formation rates.

Findings

High-mass galaxies sustain star formation via internal gas recycling.

The metallicity plateau at Z(O)=0.0013 is explained by this model.

Star formation rates align with mass loss rates from evolved stars.

Abstract

The decline of star formation in massive low-redshift galaxies, often referred to as quenching, has been attributed to a variety of factors. Some proposals suggest that erupting active galactic nuclei may strip galaxies of their interstellar medium, and thus the ability to form stars. Here, we note that, whereas star formation is universal in small, low-redshift galaxies, fractional duty cycles of star formation steadily decline in galaxies of increasing mass, although star formation may not cease entirely. We show that, when infall of gas from extragalactic space ceases, galaxies of high stellar mass appear to sustain star formation on gas liberated in mass loss from evolved low- and intermediate-mass stars admixed with occasional Type II supernova ejecta. This model quantitatively accounts for the universal limiting metallicity plateau at a ratio of oxygen to hydrogen atoms, Z(O) = n(O)/n(H) = 0.0013, characterizing high-mass intermittently star-forming galaxies. We show that, when fractional duty cycles are specifically taken into account, the star formation rates of galaxies on this plateau correspond to mass loss rates from evolving stars in rough agreement with observed estimates. Far-infrared continuum and fine-structure line observations, as well as molecular data, may soon be able to resolve whether or not low levels of sporadic star formation can be sustained indefinitely in massive galaxies.