The Universal Relation of Galactic Chemical Evolution: The Origin of the Mass-Metallicity Relation

Abstract

We examine the mass-metallicity relation for z 1.6. The mass-metallicity relation follows a steep slope with a turnover or 'knee' at stellar masses around 10 10 M ⊙ . At stellar masses higher than the characteristic turnover mass, the mass-metallicity relation flattens as metallicities begin to saturate. We show that the redshift evolution of the mass-metallicity relation depends only on evolution of the characteristic turnover mass. The relationship between metallicity and the stellar mass normalized to the characteristic turnover mass is independent of redshift. We find that the redshift independent slope of the mass-metallicity relation is set by the slope of the relationship between gas mass and stellar mass. The turnover in the mass-metallicity relation occurs when the gas-phase oxygen abundance is high enough that the amount of oxygen locked up in low mass stars is an appreciable fraction of the amount of oxygen produced by massive stars. The characteristic turnover mass is the stellar mass where the stellar-to-gas mass ratio is unity. Numerical modeling suggests that the relationship between metallicity and stellar-to-gas mass ratio is a redshift independent, universal relationship followed by all galaxies as they evolve. The mass-metallicity relation originates from this more fundamental universal relationship between metallicity and stellar-to-gas mass ratio. We test the validity of this universal metallicity relation in local galaxies where stellar mass, metallicity and gas mass measurements are available. The data are consistent with a universal metallicity relation. We derive an equation for estimating the hydrogen gas mass from measurements of stellar mass and metallicity valid for z 1.6 and predict the cosmological evolution of galactic gas masses.

Galaxy metallicity scaling relations in the EAGLE simulations

“…More recently, Schaye et al (2015) showed that the Evolution and Assembly of GaLaxies and their Environments (EAGLE, Schaye et al 2015) simulations are able to reproduce a correlation between stellar mass and gas-phase metallicity at z = 0, which agrees well with observed data (Tremonti et al 2004;Zahid et al 2014a) for the high-resolution version of those simulations. EAGLE highresolution simulations have also been found to predict an evolution of the MZR consistent with the observational trend reported by Zahid et al (2013a) (e.g.…”

“…The local M * -Z SF,gas relation Schaye et al (2015) have compared the local M * -O/H| SF,gas relation measured by Tremonti et al (2004) and Zahid et al (2014a) with results from the EAGLE intermediate-and high-resolution simulations, Ref-L100N1504 and Recal-L025N0752, respectively. The two sets of observed data are both based on SDSS data, but metallicities were obtained using different techniques.…”

“…These studies have been extended at different z by many authors in recent years (e.g. Cresci et al 2012;Hunt et al 2012;Henry et al 2013;LaraLópez, López-Sánchez & Hopkins 2013;Stott et al 2013;Cullen et al 2014;Maier et al 2014;Nakajima & Ouchi 2014;Zahid et al 2014a;Bothwell et al 2016a;Kacprzak et al 2016) but, as in the case of the MZR, the large uncertainties and diverse observational techniques involved in observational works prevent convergence towards a clear determination of these FMRs of galaxies, as discussed by Telford et al (2016).…”

On the universality of luminosity–metallicity and mass–metallicity relations for compact star-forming galaxies at redshifts 0 < z < 3

“…The mass-metallicity relation by Tremonti et al (2004) is often used as a benchmark for comparisons with similar relations obtained for low-z and high-z galaxies (e.g. Lee et al 2006;Maiolino et al 2008;Amorín et al 2010;Manucci et al 2010;Maier et al 2014;Steidel et al 2014;Zahid et al 2011Zahid et al , 2012Zahid et al , 2013Zahid et al , 2014a. However, we note that Tremonti et al (2004) selected all star-forming galaxies, including galaxies with low-excitation H ii regions, while only galaxies with high-excitation H ii regions are present in high-z samples.…”

Predicting the stellar and non-equilibrium dust emission spectra of high-resolution simulated galaxies with dart-ray

“…Tremonti et al 2004, Zahid et al 2014. In order to derive this relation, the metallicity is measured from the intensity of strong nebular line emission, while the stellar mass from the total luminosity in a particular band times a suitable massto-luminosity ratio.…”