Stellar mass, not dynamical mass nor gravitational potential, drives the mass-metallicity relationship

Abstract

The widely known relation between stellar mass and gas metallicity (mass-metallicity relation, MZR) in galaxies is often ascribed to the higher capability of more massive systems to retain metals against the action of galactic outflows. In this scenario the stellar mass would simply be an indirect proxy of the dynamical mass or of the gravitational potential. We test this scenario by using a sample of more than one thousand star-forming galaxies from the MaNGA survey for which dynamical masses have been accurately determined. By using three different methods (average dispersion, Partial Correlation Coefficients, Random Forest) we unambiguously find that the gas metallicity depends primarily and fundamentally on the stellar mass. Once the dependence on stellar mass is taken into account, there is little or no dependence on either dynamical mass or gravitational potential (and, if anything, the metallicity dependence on the latter quantities is inverted). Our result indicates that the MZR is not caused by the retention of metals in more massive galaxies. The direct, fundamental dependence of metallicity on stellar mass suggests the much simpler scenario in which the MZR is just a consequence of the stellar mass being proportional to the integral of metals production in the galaxy.

7 pages, 3 figures, Accepted for publication in MNRAS

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• The Extreme Low-mass End of the Mass-Metallicity Relation at $z\sim 7$
• Baryonic properties of nearby galaxies across the stellar-to-total dynamical mass relation
• Direct-method metallicity gradients derived from spectral stacking with SDSS-IV MaNGA
• A new perspective on the stellar Mass-Metallicity Relation of quiescent galaxies from the LEGA-C survey
• Insights on Metal Enrichment and Environmental Effect at $z\approx 5-7$ with JWST ASPIRE/EIGER and Chemical Evolution Model
• Universal bimodality in kinematic morphology and the divergent pathways to galaxy quenching
• Both Stellar Mass and Gravitational Potential Shape the Gas-Phase Metallicity
• The mass-metallicity relation at z>3 down to M_*= 10^4 M_Sun. A local perspective using the metallicity distribution of RR Lyrae stars