The stellar mass versus stellar metallicity relation of star-forming galaxies at $1.6\le z\le 3.0$ and implications for the evolution of the $\alpha$-enhancement

Abstract

We measure the relationship between stellar mass and stellar metallicity, the stellar mass--metallicity relation (MZR), for 1336 star-forming galaxies at $1.6\le z\le 3.0$ (<z>=2.2) using rest-frame far-ultraviolet spectra from the zCOSMOS-deep survey. High signal-to-noise composite spectra containing stellar absorption features are fit with population synthesis model spectra of a range of metallicity. We find stellar metallicities, which mostly reflect iron abundances, scaling as $(Z_{Fe,\ast }/Z_{Fe,\odot })=-(0.81\pm 0.01)+(0.32+0.03)\log (M_{\ast }/10^{10}{M}_{\odot })$ across the mass range of $10^9\lesssim M_{\ast }/M_{\odot }\lesssim 10^{11}$, being $\approx 6\times$ lower than seen locally at the same masses. The instantaneous oxygen-to-iron ratio ($\alpha$-enhancement) inferred using the gas-phase oxygen MZRs, is on average found to be [O/Fe]$\approx 0.47$, being higher than the local [O/Fe]$\approx 0$. The observed changes in [O/Fe] and [Fe/H] are reproduced in simple flow-through gas-regulator models with steady star-formation histories (SFHs) that follow the evolving main sequence. Our models show that the [O/Fe] is determined almost entirely by the instantaneous specific star formation rate alone while being independent of the SFHs, mass, and the gas-regulation characteristics of the systems. We find that the locations of $\sim 10^{10}{M}_{\odot }$ galaxies at z~2 in the [O/Fe]--metallicity planes are in remarkable agreement with the sequence of low-metallicity thick-disk stars in our Galaxy. This manifests a beautiful concordance between the results of Galactic archaeology and observations of high-redshift Milky Way progenitors. However, there remains a question of how and when the old metal-rich, low-$\alpha$/Fe stars seen in the bulge had formed by z~2 because such a stellar population is not seen in our data and difficult to explain in the context of our models.

Submitted to ApJ; 30 pages, 20 figures

References in corpus (29)

• The Mass-Metallicity Relation at z~2
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Constraining the Low-Mass Slope of the Star Formation Sequence at 0.5<z<2.5
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• An Objective Definition for the Main Sequence of Star-Forming Galaxies
• The Mass-Metallicity and the Fundamental Metallicity Relation revisited on a fully Te-based abundance scale for galaxies
• The Universal Relation of Galactic Chemical Evolution: The Origin of the Mass-Metallicity Relation
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies
• Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio
• The MOSDEF Survey: Mass, Metallicity, and Star-formation Rate at z~2.3
• The GIRAFFE Inner Bulge Survey (GIBS) III. Metallicity distributions and kinematics of 26 Galactic bulge fields
• The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs
• On the SFR-M${}_{\ast }$ main sequence archetypal star-formation history and analytical models
• The VANDELS survey: the stellar metallicities of star-forming galaxies at 2.5 < z < 5.0
• Stellar Absorption Line Analysis of Local Star-Forming Galaxies: The Relation Between Stellar Mass, Metallicity, Dust Attenuation and Star Formation Rate
• The imprint of clump formation at high redshift. I. A disc alpha-abundance dichotomy
• A radial age gradient in the geometrically thick disk of the Milky Way
• The NIRVANDELS Survey: a robust detection of $\alpha$-enhancement in star-forming galaxies at $z\simeq 3.4$
• GMASS Ultradeep Spectroscopy of Galaxies at redshift z~2. I. The stellar metallicity
• The MOSDEF-LRIS Survey: The Connection Between Massive Stars and Ionized Gas in Individual Galaxies at $z\sim 2$
• The Evolution of Oxygen and Magnesium in the Bulge and Disk of the Milky Way
• Rates, Progenitors and Cosmic Mix of Type Ia Supernovae
• A spectroscopic study of blue supergiant stars in the Sculptor galaxy NGC 55: chemical evolution and distance
• The age-chemical abundance structure of the Galactic disc II: $\alpha$-dichotomy and thick disc formation
• The VANDELS survey: the relation between UV continuum slope and stellar metallicity in star-forming galaxies at z~3
• On the cosmic evolution of the specific star formation rate
• Disentangling the physical parameters of gaseous nebulae and galaxies
• The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved Stellar Population Tools

Cited by in corpus (21)

• EIGER II. first spectroscopic characterisation of the young stars and ionised gas associated with strong H$\beta$ and [OIII] line-emission in galaxies at z=5-7 with JWST
• Nitrogen enhancements 440 Myr after the Big Bang: super-solar N/O, a tidal disruption event or a dense stellar cluster in GN-z11?
• The VANDELS survey: a measurement of the average Lyman-continuum escape fraction of star-forming galaxies at z=3.5
• GA-NIFS: High number of dual active galactic nuclei at z~3
• The Impact of Star-Formation-Rate Surface Density on the Electron Density and Ionization Parameter of High-Redshift Galaxies
• The SAMI galaxy survey: galaxy size can explain the offset between star-forming and passive galaxies in the mass-metallicity relationship
• Bridging Optical and Far-Infrared Emission-Line Diagrams of Galaxies from Local to the Epoch of Reionization: Characteristic High [O III] 88 $\mu \mathrm{m}$/SFR at $z>6$
• SIMBA-C: An updated chemical enrichment model for galactic chemical evolution in the SIMBA simulation
• Lyman-Alpha Escape from Low-Mass, Compact, High-Redshift Galaxies
• Dust attenuation, dust content and geometry of star-forming galaxies
• Trading oxygen for iron I: the [O/Fe] -- specific star formation rate relation of galaxies
• SDSS-IV MaNGA: the chemical co-evolution of gas and stars in spiral galaxies
• Accelerated structural evolution of galaxies in a starbursting cluster at z=2.51
• Identifying Lyα emitter candidates with Random Forest: learning from galaxies in CANDELS survey
• The JWST EXCELS Survey: gas-phase metallicity evolution at 2 < z < 8
• Probing cosmic chemical enrichment with next-generation gravitational-wave observatories
• A Global Census of Metals in the Universe
• pop-cosmos: Insights from generative modeling of a deep, infrared-selected galaxy population
• MARTA: The connection between chemical enrichment, feedback, and dust in a Wolf-Rayet galaxy at z$\sim$2
• pop-cosmos: Star formation over 12 Gyr from generative modelling of a deep infrared-selected galaxy catalogue
• Effect of dust in circumgalactic haloes on the cosmic shear power spectrum