The MOSDEF Survey: A Stellar Mass–SFR–Metallicity Relation Exists at z ∼ 2.3^∗

Abstract

We investigate the nature of the relation among stellar mass, star-formation rate, and gas-phase metallicity (the M * -SFR-Z relation) at high redshifts using a sample of 260 star-forming galaxies at z ∼ 2.3 from the MOSDEF survey. We present an analysis of the high-redshift M * -SFR-Z relation based on several emission-line ratios for the first time. We show that a M * -SFR-Z relation clearly exists at z ∼ 2.3. The strength of this relation is similar to predictions from cosmological hydrodynamical simulations. By performing a direct comparison of stacks of z ∼ 0 and z ∼ 2.3 galaxies, we find that z ∼ 2.3 galaxies have ∼ 0.1 dex lower metallicity at fixed M * and SFR. In the context of chemical evolution models, this evolution of the M * -SFR-Z relation suggests an increase with redshift of the mass-loading factor at fixed M * , as well as a decrease in the metallicity of infalling gas that is likely due to a lower importance of gas recycling relative to accretion from the intergalactic medium at high redshifts. Performing this analysis simultaneously with multiple metallicity-sensitive line ratios allows us to rule out the evolution in physical conditions (e.g., N/O ratio, ionization parameter, and hardness of the ionizing spectrum) at fixed metallicity as the source of the observed trends with redshift and with SFR at fixed M * at z ∼ 2.3. While this study highlights the promise of performing high-order tests of chemical evolution models at high redshifts, detailed quantitative comparisons ultimately await a full understanding of the evolution of metallicity calibrations with redshift.

A Tale of Two Clusters: An Analysis of Gas-phase Metallicity and Nebular Gas Conditions in Proto-cluster Galaxies at z ∼ 2

“…The predicted D16 indicator typically is ∼ 0.5 dex higher than the PP04 indicator at low masses, log(M * < 9.5. Additionally, we compared our measurements to the MOSDEF sample (Sanders et al 2018) and the previous measurements of the COSMOS protocluster and field Kacprzak et al (2015), which only used the PP04 indicator, and found similar results as our PP04 measurements ( Figure 2, top panels).…”

“…When at least one emission line shows significant sky interference, the point is unfilled. We compare to the MOSDEF metallicity measurements (Sanders et al 2018) at z ∼ 2.3, and to the ZFIRE measurements of the COSMOS proto-cluster and field in Kacprzak et al (2015). Small red arrows on the left side of each plot mark the location of solar metallicity.…”

“…We utilize the strong-line gas-phase metallicity diagnostics introduced in Pettini & Pagel (2004) (referred to herein as PP04) and the newer indicator by Dopita et al (2016) (referred to as D16). The PP04 indicator is widely used in high-redshift extragalactic astronomy (Wuyts et al 2014;Zahid et al 2014;Sanders et al 2015Sanders et al , 2018 and is not sensitive to reddening (because it utilizes a ratio of Hα to [Nii]). However it is subject to the calibration issues noted above and is sensitive to the ionization parameter and electron density of a host galaxy, as well as the presence of shock-heated gas and low-level AGN.…”

Evidence for Non-smooth Quenching in Massive Galaxies at z ∼ 1

“…If the [NII]/Hα ratio is substantially higher among our sample, the inferred η values could be overestimated. Indeed, [NII] emission from high-z galaxies appears higher than expected given their [OIII]/Hβ ratios (Steidel et al 2014;Masters et al 2014;Jones et al 2015;Shapley et al 2015, but see Sanders et al 2018). Increasing the [NII]/Hα ratio by 0.37 dex increases the predicted flux distribution, bringing models A and C in better agreement with observations.…”

The mass–metallicity and the fundamental metallicity relation revisited on a fully Te-based abundance scale for galaxies

“…Chisholm et al 2015). The MZR has been observed to hold also at redshifts out to 3 and beyond, nonetheless showing clear signs of evolution (Erb et al 2006a;Maiolino et al 2008;Mannucci et al 2009;Zahid et al 2011Zahid et al , 2014aYabe et al 2015;Ly et al 2016;Sanders et al 2018). In fact, high-z galaxies are observed to be less enriched than local ones for a given stellar mass, an effect that is more predominantly observed at low masses.…”