The ALPINE-CRISTAL-JWST Survey: The Fast Metal Enrichment of Massive Galaxies at z~5

TL;DR

The study probes metal enrichment in 18 massive galaxies at z~5 using ALPINE-CRISTAL-JWST data, extending MZR and FMR measurements to higher masses than prior JWST samples. Metallicity estimates from strong-line calibrations are validated against Te-based measurements for a subset, revealing little MZR evolution at the massive end from z~5 to cosmic noon, and a FMR with significantly larger scatter than locally, consistent with bursty star formation and variable inflows/outflows. A simple analytic regulator model with realistic metal yields and a mass-loading factor reproduces the observed MZR and the FMR scatter, while cosmological simulations largely agree in trend but differ in amplitude and scatter at low masses. Tracing progenitors to z>10 and descendants to z=0 with the DUSTY-GAEA model shows rapid early metal buildup and evolution toward super-solar metallicities for massive galaxies, illustrating a coherent picture where early enrichment sets the stage for mature metal growth and eventual quenching. These results provide constraints on feedback, inflow metallicity, and star-formation histories in the early universe and guide interpretation of future JWST/ALMA observations and simulations.

Abstract

We present the stellar mass-metallicity relation (MZR) and mass-metallicity-star formation relation ("fundamental metallicity relation"; FMR) of 18 massive (log(M/M$_\odot$) = 9.5-11) main-sequence galaxies at z~5 from the ALPINE-CRISTAL-JWST sample. This sample complements recent studies by JWST at up to two orders of magnitude lower stellar masses. The metallicities are derived using strong optical lines, and verified by temperature-based oxygen abundance measurements for five galaxies for which faint auroral lines are detected. We find little evolution at the massive end of the MZR between z~5 and cosmic noon at z~2, suggesting a fast metal enrichment at early times. The FMR at z=5 exhibits a 5x larger scatter (preferentially to lower metallicities) compared the local FMR relation. This scatter can be explained by a bursty star formation and the direct build-up of metals in early galaxies as well as differences in age and outflow efficiencies. Capitalizing on all available samples, we find that the observed MZR and FMR over three orders of stellar mass is generally in good agreement with results from cosmological simulation, although some underestimate the metal enrichment at low stellar masses. This may be due to too efficient metal-rich outflows. We show that the ALPINE-CRISTAL-JWST galaxies likely joined the current FMR at z~10 and will evolve into massive (log(M/M$_\odot$)~11.4) galaxies with super-solar metallicities by z=0.

Figures (10)

• Figure 1: The stellar mass vs. metallicity relation (MZR) at $z\sim5$. Top: The observed MZR of the $z\sim5$ ALPINE-CRISTAL-JWST sample (large open circles; six type 1 broad-line AGN candidates identified by ren25 are indicated in gray). Other observations with JWST at $z=4-6$nakajima23morishita24curti24sarkar25heintz25 and at $z=6.5-7.5$rowland25 are also shown. The thick dashed line shows a fit to all $z=4-6$ data (see Equation \ref{['eq:mzr']} and Table \ref{['tab:mzrfit']}). The contours show results from the cosmological simulations SERRApallottini22, FIRE-2ma16marszewski24, and NewHorizondubois21. Dotted, dashed, dot-dashed, and thin solid line shows the MZR parameterizations by maiolino08 at $z<3.5$. Bottom: The same observational data (black crosses) compared to other cosmological simulations; IllustrisTNGhirschmann23, SPHINX$^{20}$rosdahl18rosdahl22katz23, DUSTY-GAEAosman25, and THESAN-ZOOMkannan25. In addition, we show other analytical models from pantoni19 (green backward-hatched), pallottini25 (orange vertical-hatched), and liulunjun24 (gray shaded).
• Figure 2: The stellar mass, metallicity, and SFR relation ("fundamental metallicity relation", FMR). Left: Data are shown at $z=0$ from SDSS (small circles), at $z\sim2$ from the FMOS survey silverman15kashino17, and from the ALPINE-CRISTAL-JWST survey at $z\sim5$ (large circles; this work). The data are compared to an equilibrium gas-regulator model (see Equation \ref{['eq:fmr']}) from lilly13maier14onodera16, calibrated by kashino17 to the SDSS $z=0$ measurements (colored lines). The symbols and lines are color-coded by stellar mass on the same scale. Right: The collapsed FMR assuming $\mu_0=0.66$andrews13. The ALPINE-CRISTAL-JWST sample at $z\sim5$ is shown as large circles (type 1 AGN candidates from ren25 indicated in gray). Other literature data are shown at $z=4-6$ and $z>6$nakajima23curti24morishita24sarkar25heintz25 as well as from the REBELS-IFU survey rowland25. The small blue points are data at $z=0$andrews13 with the corresponding fit shown as dashed gray line. The dot-dashed gray line shows the $z=0$ parameterization by curti20. The gray band shows the $1\sigma$ percentiles of the literature and ALPINE-CRISTAL-JWST data at $z=4-6$.
• Figure 3: Illustration of the metal build-up from our simple analytical model. We assume a starburst forming $5\times10^9\,{\rm M_\odot}$ within $100\,{\rm Myr}$ at a rate of $50\,{\rm M_\odot\,yr^{-1}}$ (hatched area). Top: Instantaneous metal ejection rate (${ \dot{M}_{\rm ej,Z}}$) over time from type II SNe and AGB stars for carbon (dashed), nitrogen (dotted), oxygen (solid), and their sum (thick solid). Bottom: Cumulative ejected metal mass over time.
• Figure 4: The MZR reproduced by our analytical model at $z\sim5$ (see Section \ref{['sec:discussionanalytical']} for details). Model galaxies are color-coded by their age. ALPINE-CRISTAL-JWST galaxies are shown as large symbols with same color code and other literature data are shown as gray squares (see also Figure \ref{['fig:mzr']}). Our model captures well the range of observations and visualizes the fast metal enrichment. The upper envelope of the MZR is set by maximally old model galaxies (red). The observed galaxy ages correlate well with the model ages. The three gray swaths show model track ranges for two different outflow efficiencies including the nominal mass-loading factor from mitchell20. Lower outflow efficiencies increase the metal content at a given stellar mass. The width of the swaths shows a range in the metallicity of the inflowing gas from metal free ($r_{\rm Z} = 0$) to $50\%$ ($r_{\rm Z} = 0.5$) of the metallicity of the ISM gas.
• Figure 5: Scatter of the FMR as a function of $\mu$ for different assumption of burstiness of the SFH. The SFH is described by a burstiness amplitude ($\sigma_{\rm MS}$, different panels) and a correlation timescale ($\tau_{\rm break}$, shades of blue). The observed FMR scatter (deconvolved by measurement errors) at $z\sim5$ and $z=0$ is shown in light and dark gray, respectively. We also show the scatter derived from the analytical models from liulunjun24 (long-dashed line) and pallottini25 (dotted line).