Astrophys. J., 877, 6-6 (2019/May-3)
A characteristic mass scale in the mass-metallicity relation of galaxies.
BLANC G.A., LU Y., BENSON A., KATSIANIS A. and BARRAZA M.
Abstract (from CDS):
We study the shape of the gas-phase mass-metallicity relation (MZR) of a combined sample of present-day dwarf and high-mass star-forming galaxies using IZI, a Bayesian formalism for measuring chemical abundances presented in a previous publication. We observe a characteristic stellar mass scale at M* ≃ 109.5 M☉, above which the inter-stellar medium undergoes a sharp increase in its level of chemical enrichment. In the 106-109.5 M☉ range the MZR follows a shallow power law (Z∝M*^α^) with slope α = 0.14 ± 0.08. Approaching M* ≃ 109.5 M☉ the MZR steepens significantly, showing a slope of α = 0.37 ± 0.08 in the 109.5–1010.5M☉ range, and a flattening toward a constant metallicity at higher stellar masses. This behavior is qualitatively different from results in the literature that show a single power-law MZR toward the low-mass end. We thoroughly explore systematic uncertainties in our measurement, and show that the shape of the MZR is not induced by sample selection, aperture effects, a changing N/O abundance, the adopted methodology to construct the MZR, secondary dependences on star formation activity, or diffuse ionized gas contamination, but rather on differences in the method used to measure abundances. High-resolution hydrodynamical simulations of galaxies can qualitatively reproduce our result, and suggest a transition in the ability of galaxies to retain their metals for stellar masses above this threshold. The MZR characteristic mass scale also coincides with a transition in the scale height and clumpiness of cold gas disks, and a typical gas fraction below which the efficiency of star formation feedback for driving outflows is expected to decrease sharply.
© 2019. The American Astronomical Society. All rights reserved.
galaxies: abundances - galaxies: evolution - galaxies: fundamental parameters - galaxies: ISM - ISM: abundances - ISM: structure
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