Fundamental Metallicity Relation Research Articles

Does the fundamental metallicity relation evolve with redshift? I: The correlation between offsets from the mass-metallicity relation and star formation rate

Does the fundamental metallicity relation evolve with redshift? I: The correlation between offsets from the mass-metallicity relation and star formation rate

The MUSE Ultra Deep Field (MUDF). V. Characterizing the Mass–Metallicity Relation for Low-mass Galaxies at z ∼ 1–2

Using more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope’s (HST) Wide Field Camera 3 and the Very Large Telescope’s Multi Unit Spectroscopic Explorer, we extend the gas-phase mass–metallicity relation (MZR) at z ≈ 1–2 down to stellar masses of M ⋆ ≈ 107.5 M ⊙. The sample reaches 6 times lower in stellar mass and star formation rate (SFR) than previous HST studies at these redshifts, and we find that galaxy metallicities decrease to log(O/H) + 12 ≈ 7.8 ± 0.1 (15% solar) at log(M ⋆/M ⊙) ≈ 7.5, without evidence of a turnover in the shape of the MZR at low masses. We validate our strong-line metallicities using the direct method for sources with [O iii] λ4363 and [O iii] λ1666 detections, and find excellent agreement between the techniques. The [O iii] λ1666-based metallicities double existing measurements with a signal-to-noise ratio ≥ 5 for unlensed sources at z > 1, validating the strong-line calibrations up to z ∼ 2.5. We confirm that the MZR resides ∼0.3 dex lower in metallicity than local galaxies and is consistent with the fundamental metallicity relation if the low-mass slope varies with SFR. At lower redshifts (z ∼ 0.5) our sample reaches ∼0.5 dex lower in SFR than current calibrations and we find enhanced metallicities that are consistent with extrapolating the MZR to lower SFRs. Finally, we detect only an ∼0.1 dex difference in the metallicities of galaxies in groups versus isolated environments. These results are based on robust calibrations and reach the lowest masses and SFRs that are accessible with HST, providing a critical foundation for studies with the Webb and Roman Space Telescopes.

JADES: Insights into the low-mass end of the mass–metallicity–SFR relation at 3 < z < 10 from deep JWST/NIRSpec spectroscopy

We analysed the gas-phase metallicity properties of a sample of low-stellar-mass (log M⋆/M⊙ ≲ 9) galaxies at 3 < z < 10 observed with JWST/NIRSpec as part of the JADES programme in its deep GOODS-S tier. By combining this sample with more massive galaxies at similar redshifts from other programmes, we study the scaling relations between stellar mass (M⋆), oxygen abundance (O/H), and star-formation rate (SFR) for 146 galaxies spanning three orders of magnitude in stellar mass and out to the epoch of early galaxy assembly. We find evidence for a shallower slope at the low-mass end of the mass–metallicity relation (MZR), with 12+log(O/H) = (7.72 ± 0.02) + (0.17 ± 0.03) log(M⋆/108 M⊙), in good agreement with the MZR probed by local analogues of high-redshift systems, such as the ‘Green Pea’ and ‘Blueberry’ galaxies. The inferred slope is well matched by models including ‘momentum-driven’ supernova (SN) winds, suggesting that feedback mechanisms in dwarf galaxies (and at high z) might be different from those in place at higher masses. The evolution in the normalisation is observed to be relatively mild compared to previous determinations of the MZR at z ∼ 3 (∼0.1 − 0.2 dex across the explored mass regime). We observe a deviation from the local fundamental metallicity relation (FMR) for our sample at high redshift, especially at z > 6, with galaxies significantly less enriched than predicted given their M⋆ and SFR (with a median offset in log(O/H) of ∼0.5 dex, significant at ∼5σ). These observations are consistent with an enhanced stochasticity in the gas accretion and star-formation history of high-redshift systems, prompting us to reconsider the nature of the relationship between M⋆, O/H, and SFR in the early Universe.

The mass–metallicity and fundamental metallicity relations in non-AGN and AGN-host galaxies

ABSTRACT Galaxies’ stellar masses, gas-phase oxygen abundances (metallicity), and star formation rates (SFRs) obey a series of empirical correlations, most notably the mass–metallicity relation (MZR) and fundamental metallicity relation (FZR), which relates oxygen abundance to a combination of stellar mass and SFR. However, due to the difficulty of measuring oxygen abundances and SFRs in galaxies that host powerful active galactic nuclei (AGN), to date it is unknown to what extent AGN-host galaxies also follow these correlations. In this work, we apply Bayesian methods to the MaNGA integral field spectrographic (IFS) survey that allow us to measure oxygen abundances and SFRs in AGN hosts, and use these measurements to explore how the MZR and FZR differ between galaxies that do and do not host AGN. We find similar MZRs at stellar masses above $10^{10.5} \, \mathrm{M}_\odot$, but that at lower stellar masses AGN hosts show up to $\sim 0.2$ dex higher oxygen abundances. The offset in the FZR is significantly smaller, suggesting that the larger deviation in the MZR is a result of AGN-host galaxies having systematically lower SFRs at fixed stellar mass. However, within the AGN-host sample there is little correlation between SFR and oxygen abundance. These findings support a scenario in which an AGN can halt efficient gas accretion, which drives non-AGN host galaxies to both higher SFR and lower oxygen abundance, resulting in the galaxy evolving off the star-forming main sequence (SFMS). As a consequence, as the SFR declines for an individual system its metallicity remains mostly unchanged.

A comparative study of the fundamental metallicity relation

Aims. We aim to investigate the influences on the evolution of the fundamental metallicity relation of different selection criteria. Methods. We used 5 487 star-forming galaxies at a median redshift of z ≈ 0.63 extracted from the VIMOS Public Extragalactic Redshift Survey (VIPERS) and 143 774 comparison galaxies in the local Universe from the GALEX-SDSS-WISE Legacy Catalog. We employed two families of methods: parametric and nonparametric. In the parametric approaches, we compared the fundamental metallicity relation projections plagued by observational biases on differently constructed control samples at various redshifts. Then, we compare the metallicity difference between different redshifts in stellar mass-star formation rate bins. In the nonparametric approach, we related the metallicity and the normalized specific star formation rate (sSFR). To compare galaxies with the same physical properties, we normalized the sSFR of our samples according to the median value at median redshift z ≈ 0.09. Then, the galaxies with the same distance from the star-forming main sequence at their respective redshifts were compared when the sSFR is normalized according to the expected values from their respective star-forming main sequences. Results. The methodologies implemented to construct fair, complete samples for studying the mass-metallicity relation and the fundamental metallicity relation produced consistent results showing a small but still statistically significant evolution of both relations up to z ≈ 0.63. In particular, we observed a systematic trend where the median metallicity of the sample at z = 0.63 is lower than that of the local sample at the same stellar mass and star formation rate. The average difference in the metallicity of the low and intermediate redshifts is approximately 1.8 times the metallicity standard deviation of the median of the intermediate redshift sample in stellar mass-star formation rate bins. We confirmed this result using the Kolmogorov-Smirnov test. When we applied the stellar mass-completeness criterion to catalogs, the metallicity difference in redshifts decreased to approximately 0.96 times the metallicity standard deviation of the median, and thus it was not statistically significant. The limited area of the FMR surface explored once the stellar mass-completeness criterion is applied might dominate this difference reduction, leaving out the area where the difference between the two samples is the highest. A careful reading of the results and their underlying selection criteria is crucial in studies of the mass-metallicity and fundamental metallicity relations. Conclusions. When studying the mass-metallicity and fundamental metallicity relations, we recommend using the nonparametric approach, which provides similar results compared to parametric prescriptions, is easier to use, and is clear to interpret. The nonparametric methodology provides a convenient way to compare physical properties, with a smaller impact on observational selection biases.

More fundamental than the fundamental metallicity relation

Context One of the most fundamental scaling relations in galaxies is observed between metallicity and stellar mass – the mass-metallicity relation (MZR) – although recently a stronger dependence of the gas-phase metallicity with the galactic gravitational potential (ΦZR) has been reported. Further dependences of metallicity on other galaxy properties have been revealed, with the star formation rate (SFR) being one of the most studied and debated secondary parameters in the relation (the so-called fundamental metallicity relation). Aims. In this work we explore the dependence of the gas-phase metallicity residuals from the MZR and ΦZR on different galaxy properties in the search for the most fundamental scaling relation in galaxies. Methods. We applied a random forest regressor algorithm on a sample of 3430 nearby star-forming galaxies from the SDSS-IV MaNGA survey. Using this technique, we explored the effect of 147 additional parameters on the global oxygen abundance residuals obtained after subtracting the MZR. Alternatively, we followed a similar approach with the metallicity residuals from the ΦZR. Results. The stellar metallicity of the galaxy is revealed as the secondary parameter in both the MZR and the ΦZR, ahead of the SFR. This parameter reduces the scatter in the relations ∼10 − 15%. We find the 3D relation between gravitational potential, gas metallicity, and stellar metallicity to be the most fundamental metallicity relation observed in galaxies.

Dwarf Galaxies Show Little ISM Evolution from z ∼ 1 to z ∼ 0: A Spectroscopic Study of Metallicity, Star Formation, and Electron Density

We present gas-phase metallicity measurements for 583 emission line galaxies at 0.3 < z < 0.85, including 388 dwarf galaxies with , and explore the dependence of the metallicity on the stellar mass and star formation (SF) properties of the galaxies. Metallicities are determined through the measurement of emission lines in very deep (∼7 hr exposure) Keck/DEIMOS spectra taken primarily from the HALO7D survey. We measure metallicity with three strong-line calibrations (O3Hβ, R23, and O3O2) for the overall sample, as well as with the faint [Ne iii]λ3869 and [O iii]λ4363 emission lines for 112 and 17 galaxies where robust detections were possible. We construct mass–metallicity relations (MZR) for each calibration method, finding MZRs consistent with other strong-line results at comparable redshift, as well as with z ∼ 0 galaxies. We quantify the intrinsic scatter in the MZR as a function of mass, finding it increases with lower stellar mass. We also measure a weak but significant correlation between increased MZR scatter and higher specific star formation rate (SFR). We find a weak influence of SFR in the fundamental metallicity relation as well, with an SFR coefficient of α = 0.21. Finally, we use the flux ratios of the [O ii]λ λ 3727,3729 doublet to calculate gas electron density in ∼1000 galaxies with as a function of redshift. We measure low electron densities (n e ∼ 25 cm−3) for z < 1 galaxies, again consistent with z ≈ 0 conditions, but measure higher densities (n e ∼ 100 cm−3) at z > 1. These results all suggest that there is little evolution in star-forming interstellar medium conditions from z ∼ 1 to z = 0, confirmed with a more complete sample of low-mass galaxies than has previously been available in this redshift range.

Quasar Sightline and Galaxy Evolution (QSAGE) – III. The mass–metallicity and fundamental metallicity relation of z ≈ 2.2 galaxies

ABSTRACT We present analysis of the mass–metallicity relation (MZR) for a sample of 67 [O iii]-selected star-forming (SF) galaxies at a redshift range of z = 1.99−2.32 (zmed = 2.16) using Hubble Space Telescope Wide Field Camera 3 grism spectroscopy from the Quasar Sightline and Galaxy Evolution survey. Metallicities were determined using empirical gas-phase metallicity calibrations based on the strong emission lines [O ii]3727, 3729, [O iii]4959, 5007 and Hβ. SF galaxies were identified, and distinguished from active-galactic nuclei, via Mass–Excitation diagrams. Using z ∼ 0 metallicity calibrations, we observe a negative offset in the z = 2.2 MZR of ≈−0.51 dex in metallicity when compared to locally derived relationships, in agreement with previous literature analysis. A similar offset of ≈−0.46 dex in metallicity is found when using empirical metallicity calibrations that are suitable out to z ∼ 5, though our z = 2.2 MZR, in this case, has a shallower slope. We find agreement between our MZR and those predicted from various galaxy evolution models and simulations. Additionally, we explore the extended fundamental metallicity relation (FMR) which includes an additional dependence on star formation rate. Our results consistently support the existence of the FMR, as well as revealing an offset of 0.28 ± 0.04 dex in metallicity compared to locally derived relationships, consistent with previous studies at similar redshifts. We interpret the negative correlation with SFR at fixed mass, inferred from an FMR existing for our sample, as being caused by the efficient accretion of metal-poor gas fuelling SFR at cosmic noon.

Physics-informed neural networks in the recreation of hydrodynamic simulations from dark matter

ABSTRACT Physics-informed neural networks have emerged as a coherent framework for building predictive models that combine statistical patterns with domain knowledge. The underlying notion is to enrich the optimization loss function with known relationships to constrain the space of possible solutions. Hydrodynamic simulations are a core constituent of modern cosmology, while the required computations are both expensive and time-consuming. At the same time, the comparatively fast simulation of dark matter requires fewer resources, which has led to the emergence of machine learning algorithms for baryon inpainting as an active area of research; here, recreating the scatter found in hydrodynamic simulations is an ongoing challenge. This paper presents the first application of physics-informed neural networks to baryon inpainting by combining advances in neural network architectures with physical constraints, injecting theory on baryon conversion efficiency into the model loss function. We also introduce a punitive prediction comparison based on the Kullback–Leibler divergence, which enforces scatter reproduction. By simultaneously extracting the complete set of baryonic properties for the simba suite of cosmological simulations, our results demonstrate improved accuracy of baryonic predictions based on dark matter halo properties and successful recovery of the fundamental metallicity relation, and retrieve scatter that traces the target simulation’s distribution.

Expanding on the fundamental metallicity relation in dwarf galaxies with MUSE

The mass–metallicity relation (MZR) represents one of the most important scaling relations in the context of galaxy evolution, comprising a positive correlation between stellar mass and metallicity (Z). The fundamental metallicity relation (FMR) introduces a new parameter into the dependence, namely, the star formation rate (SFR). While several studies have found that Z is anti-correlated with the SFR at a fixed mass, the validity of this statement has been questioned extensively and no widely accepted consensus has been reached thus far. With this work, we investigate the FMR in nine nearby, spatially resolved, dwarf galaxies, using gas diagnostics on integral-field spectroscopic data of the Multi Unit Spectroscopic Explorer (MUSE), pushing such investigations to lower galaxy masses and higher resolutions. We find that both the MZR and FMR exhibit different behaviours within different star-forming regions of the galaxies. We find that the SFR surface-density-and-metallicity anti-correlation is tighter in the low-mass galaxies of our sample. For all the galaxies considered, we find a SFR surface-density-and-stellar-mass surface-density correlation. We propose that the main reason behind these findings is connected to the accretion mechanisms of the gas fuelling star formation, namely: low-mass, metal-poor galaxies accrete pristine gas from the intergalactic medium, while in more massive and metal-enriched systems, the gas responsible for star formation is recycled from previous star-forming episodes.

The Mass–Metallicity Relation of Dwarf Galaxies at Cosmic Noon from JWST Observations

We present a study of the mass–metallicity relation (MZR) of 51 dwarf galaxies (M ⋆ ≈ 106.5–109.5 M ⊙) at z = 2–3 from the A2744 and SMACS J0723-3732 galaxy cluster fields. These dwarf galaxies are identified and confirmed by deep JWST/NIRISS imaging and slitless grism spectroscopic observations. By taking advantage of the superior performance of JWST and the gravitational lensing effect, we extend the previous MZR relation at z = 2–3 to a much lower-mass regime down by ≈2.5 orders of magnitude as compared with previous studies. We find that the MZR has a shallower slope at the low-mass end (M ⋆ < 109 M ⊙), with a slope turnover point of ≈109 M ⊙. This implies that the dominating feedback processes in dwarf galaxies may be different from that in massive galaxies. From z = 3, to z = 2, the metallicity of the dwarf galaxies is enhanced by ≈0.09 dex for a given stellar mass, consistent with the mild evolution found in galaxies with higher mass. Furthermore, we confirm the existence of a fundamental metallicity relation (FMR) between the gas-phase metallicity, stellar mass, and star formation rate in dwarf galaxies at z = 2–3. Our derived FMR, which has no significant redshift evolution, can be used as a benchmark to understand the origin of the anticorrelation between the star formation rate and metallicity of dwarf galaxies in the high-z Universe.

Ionized gas kinematics and chemical abundances of low-mass star-forming galaxies at z ∼ 3

Context. Feedback from massive stars plays a crucial role in regulating the growth of young star-forming galaxies (SFGs) and in shaping their interstellar medium (ISM). This feedback contributes to the removal and mixing of metals via galactic outflows and to the clearance of neutral gas, which facilitates the escape of ionizing photons. Aims. Our goal is to study the impact of stellar feedback on the chemical abundances of the ISM in a sample of SFGs with strong emission lines at z ∼ 3. Methods. We selected 35 low-mass SFGs (7.9 &lt; log(M⋆/M⊙) &lt; 10.3) from deep spectroscopic surveys based on their CIII]λ1908 emission. We used new follow-up near-infrared (NIR) observations to examine their rest-optical emission lines and to identify ionized outflow signatures through broad emission line wings detected after Gaussian modeling of [OIII]λλ4959,5007 profiles. We characterized the gas-phase metallicity and carbon-to-oxygen (C/O) abundance of the galaxies using a Te-based method via the OIII]λ1666/[OIII]λ5007 ratio and photoionization models. Results. We find line ratios and rest-frame equivalent widths (EWs) characteristic of high-ionization conditions powered by massive stars. Our sample displays a mean rest-frame EW([OIII]λ5007) of ∼560 Å, while about 15% of the SFGs show EW([OIII]λλ4959,5007) &gt; 1000 Å and EW(CIII]) &gt; 5 Å, closely resembling those now seen in epoch of reionization (EoR) galaxies with the James Webb Space Telescope. We find high Te values, which imply low gas-phase metallicities 12+log(O/H) ∼ 7.5–8.5 (mean of 17% solar) and C/O abundances from 23% to 128% solar, with no apparent increasing trend with metallicity. Our sample follows the mass-metallicity relation at z ∼ 3, with some galaxies showing lower gas-phase metallicities. This results in significant deviations from the fundamental metallicity relation. From our [OIII]λλ4959,5007 line profile modeling, we find that 65% of our sample shows an outflow component, which is found both blue- or redshifted relative to the ionized gas systemic velocity, and the mean maximum velocities are vmax ∼ 280 km s−1. We find a weak correlation between vmax and the star formation rate surface density (ΣSFR) of vmax = (2.41 ± 0.03) × ΣSFR(0.06 ± 0.03). Moreover, we find that the mass-loading factor μ of our galaxy sample is typically lower than in more massive galaxies from the literature, but it is higher than in typical local dwarf galaxies. In the stellar mass range covered by our sample, we find that μ increases with ΣSFR. This suggests that for a given stellar mass, denser starbursts in low-mass galaxies produce stronger outflows. Our results complement the picture drawn by similar studies at lower redshift, suggesting that the removal of ionized gas in low-mass SFGs driven by stellar feedback is regulated by their stellar mass and by the strength and concentration of their star formation, that is, ΣSFR.

The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon∗ ∗ The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of

We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲ z ≲ 2.6 (z mean = 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of and a median star formation rate of . We measure the faint electron-temperature-sensitive [O iii] λ4363 emission line at 2.5σ (4.1σ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of (). We investigate the applicability at high z of locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixed M *, our composite is well represented by the z ∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixed M * and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [O ii] λ3729/[O ii] λ3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of () when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies at z ∼ 2.

A solar metallicity galaxy at z &amp;gt; 7? Possible detection of the [N ii] 122 μm and [O iii] 52 μm lines

ABSTRACT We present the first detection of the [N ii] 122 $\mu$m and [O iii] 52 $\mu$m lines for a reionization-epoch galaxy. Based on these lines and previous [C ii] 158 $\mu$m and [O iii] 88 $\mu$m measurements, using two different radiative transfer models of the interstellar medium, we estimate an upper limit on electron density of ≲500 cm−3 and an approximate gas-phase metallicity of Z/Z⊙ ∼ 1.1 ± 0.2 for A1689-zD1, a gravitationally lensed dusty galaxy at z = 7.133. Other measurements or indicators of metallicity so far in galaxy interstellar media at z ≳ 6 are typically an order of magnitude lower than this. The unusually high metallicity makes A1689-zD1 inconsistent with the fundamental metallicity relation, although there is likely significant dust obscuration of the stellar mass, which may partly resolve the inconsistency. Given a solar metallicity, the dust-to-metals ratio is a factor of several lower than expected, hinting that galaxies beyond z ∼ 7 may have lower dust formation efficiency. Finally, the inferred nitrogen enrichment compared to oxygen, on which the metallicity measurement depends, indicates that star formation in the system is older than about 250 Myr, pushing the beginnings of this galaxy to z &amp;gt; 10.

Constraints on galactic outflows from the metallicity–stellar mass–SFR relation of EAGLE simulation andSDSSgalaxies

ABSTRACTStellar feedback-driven outflows regulate the stellar formation and chemical enrichment of galaxies, yet the underlying dependence of mass outflow rate on galaxy properties remains largely unknown. We develop a simple yet comprehensive non-equilibrium chemical evolution model (NE-CEM) to constrain the mass-loading factor η of outflows using the metallicity-stellar mass–SFR relation observed by Sloan Digital Sky Survey (SDSS) at z = 0. Our NE-CEM predicts the chemical enrichment by explicitly tracking both the histories of star formation and mass-loading. After exploring the eagle simulation, we discover a compact yet flexible model that accurately describes the average star formation histories of galaxies. Applying a novel method of chemically measuring η to eagle, we find η can be parametrized by its dependence on stellar mass and specific SFR as $\log \eta \propto M_*^{\alpha }s{\mathrm{SFR}}^{\beta }$, with α = − 0.12 and β = 0.32 in eagle. Our chemically inferred η agrees remarkably well with the kinematic measurements by Mitchell et al. After extensive tests with eagle, we apply an NE-CEM Bayesian analysis to the SDSS data, yielding a tight constraint of $\log (\eta /0.631) = 0.731{\pm }0.002\times (M_*/10^{9.5}\, \mathrm{M}_{\odot })^{-0.222\pm 0.004} (s{\mathrm{SFR}}/10^{-9.5}\, \mathrm{yr}^{-1})^{0.078\pm 0.003}$, in good agreement with the down-the-barrel measurements. Our best-fitting NE-CEM not only accurately describes the metallicity-stellar mass–SFR relation at z = 0, but also successfully reproduce the so-called ‘fundamental metallicity relation’ at higher redshifts. Our results reveal that different galaxies form stars and enrich their gas in a non-equilibrium but strikingly coherent fashion across cosmic time.

MusE GAs FLOw and Wind (MEGAFLOW) IX. The impact of gas flows on the relations between the mass, star formation rate, and metallicity of galaxies

ABSTRACTWe study the link between gas flow events and key galaxy scaling relations: the relations between star formation rate (SFR) and stellar mass (the main sequence, MS); gas metallicity and stellar mass (the mass–metallicity relation, MZR); and gas metallicity, stellar mass, and SFR (the fundamental metallicity relation, FMR). Using all star-forming galaxies (SFGs) in the 22 MUSE fields of the MusE GAs FLOw and Wind (MEGAFLOW) survey, we derive the MS, MZR, and FMR scaling relations for 385 SFGs with $M_\star = 10^{8} - 10^{11.5}\, {\rm M}_\odot$ at redshifts 0.35 &amp;lt; z &amp;lt; 0.85. Using the MUSE data and complementary X-Shooter spectra at 0.85 &amp;lt; z &amp;lt; 1.4, we determine the locations of 21 SFGs associated with inflowing or outflowing circumgalactic gas (i.e. with strong Mg ii absorption in background quasar spectra) relative to these scaling relations. Compared to a control sample of galaxies without gas flows (i.e. without Mg ii absorption within 70 kpc of the quasar), SFGs with inflow events (i.e. Mg ii absorption along the major axis) are preferentially located above the MS, while SFGs with outflow events (i.e. Mg ii absorption along the minor axis) are preferentially more metal rich. Our observations support the scenario in which gas accretion increases the SFR while diluting the metal content and where circumgalactic outflows are found in more metal-rich galaxies.

CO Emission, Molecular Gas, and Metallicity in Main-sequence Star-forming Galaxies at z ∼ 2.3* *The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support

We present observations of CO(3−2) in 13 main-sequence z = 2.0–2.5 star-forming galaxies at that span a wide range in metallicity (O/H) based on rest-optical spectroscopy. We find that /SFR decreases with decreasing metallicity, implying that the CO luminosity per unit gas mass is lower in low-metallicity galaxies at z ∼ 2. We constrain the CO-to-H2 conversion factor (α CO) and find that α CO inversely correlates with metallicity at z ∼ 2. We derive molecular gas masses (M mol) and characterize the relations among M *, SFR, M mol, and metallicity. At z ∼ 2, M mol increases and the molecular gas fraction (M mol/M *) decreases with increasing M *, with a significant secondary dependence on SFR. Galaxies at z ∼ 2 lie on a near-linear molecular KS law that is well-described by a constant depletion time of 700 Myr. We find that the scatter about the mean SFR−M *, O/H−M *, and M mol−M * relations is correlated such that, at fixed M *, z ∼ 2 galaxies with larger M mol have higher SFR and lower O/H. We thus confirm the existence of a fundamental metallicity relation at z ∼ 2, where O/H is inversely correlated with both SFR and M mol at fixed M *. These results suggest that the scatter of the z ∼ 2 star-forming main sequence, mass–metallicity relation, and M mol–M * relation are primarily driven by stochastic variations in gas inflow rates. We place constraints on the mass loading of galactic outflows and perform a metal budget analysis, finding that massive z ∼ 2 star-forming galaxies retain only 30% of metals produced, implying that a large mass of metals resides in the circumgalactic medium.

The metallicity’s fundamental dependence on both local and global galactic quantities

ABSTRACT We study the scaling relations between gas-phase metallicity, stellar mass surface density (Σ*), star formation rate surface density (ΣSFR), and molecular gas surface density ($\Sigma _{{\rm H}_2}$) in local star-forming galaxies on scales of a kpc. We employ optical integral field spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, and ALMA data for a subset of MaNGA galaxies. We use partial correlation coefficients and Random Forest regression to determine the relative importance of local and global galactic properties in setting the gas-phase metallicity. We find that the local metallicity depends primarily on Σ* (the resolved mass–metallicity relation, rMZR), and has a secondary anticorrelation with ΣSFR (i.e. a spatially resolved version of the ‘Fundamental Metallicity Relation’, rFMR). We find that $\Sigma _{{\rm H}_2}$ is less important than ΣSFR in determining the local metallicity. This result indicates that gas accretion, resulting in local metallicity dilution and local boosting of star formation, is unlikely to be the primary origin of the rFMR. The local metallicity depends also on the global properties of galaxies. We find a strong dependence on the total stellar mass (M*) and a weaker (inverse) dependence on the total SFR. The global metallicity scaling relations, therefore, do not simply stem out of their resolved counterparts; global properties and processes, such as the global gravitational potential well, galaxy-scale winds and global redistribution/mixing of metals, likely contribute to the local metallicity, in addition to local production and retention.

Morpho-kinematics of MACS J0416.1-2403 low-mass galaxies

We use optical integral field spectroscopy from VLT/MUSE, as well as photometric observations from Hubble Space Telescope and VLT/HAWK-I, to study the morpho-kinematics of 17 low-mass (log(M/M⊙) &lt; 9.5) MACS J0416.1-2403 cluster galaxies at R200 and five field galaxies with a redshift of z ∼ 0.4. By measuring fluxes of strong emission lines from the MUSE data, we have recovered the star formation rates, gas-phase metallicities, and spatially resolved gas kinematics, and we have also investigated the ionising mechanisms. We have analysed the structure and morphology of the galaxies from the optical and infrared photometric data, performing a multi-component decomposition into a bulge and a disk. The spatially resolved gas velocity fields of the cluster members and field galaxies were modelled using a 3D approach, which allowed us to retrieve their intrinsic gas kinematics, including the maximum rotation velocity and velocity dispersion. This enabled us to study scaling relations such as the Tully–Fisher and the stellar mass–S0.5 relation for low-mass galaxies in different environments and to search for signatures of cluster-specific processes using disturbed gas velocity fields as tracers. Most galaxies from our sample fall in the star-forming and composite region in the diagnostic diagram, which allows for the ionising sources in a galaxy to be disentangled. The cluster and field population can be classified as star-forming main-sequence galaxies, with only a sub-sample of four quenched systems. We observe significant scatter for the cluster galaxies in the mass-metallicity plane, and the lowest-mass systems deviate from the predictions of the fundamental metallicity relation, showing higher metallicities, whereas the higher-mass ones are in accordance with the model predictions. This might hint at the cutoff of pristine gas inflow and/or the removal of the hot halo gas as the mechanisms driving these offsets. Our morpho-kinematic analysis reveals a sub-sample of dwarfs with maximum velocities vmax &lt; 50 km s−1 and vmax, gas/σgas &lt; 1, which depart from the Tully–Fisher relation. This might indicate that their interstellar medium is affected by external environmental processes, such as ram pressure stripping. However, ∼30% of the cluster galaxies have rotation-dominated gas disks and follow the Tully–Fisher relation within 1σ. Using the S0.5 parameter, which links the dynamical support of ordered motions with that of random motions, we can differentiate between galaxies affected by gravitational processes and systems affected by hydrodynamical ones. In the stellar mass–S0.5 plane, both cluster and field galaxies follow a tight sequence, with only a sub-population of five galaxies strongly departing (&gt; 4σ) from this relation, showing high σgas values. Both the morphology and kinematics of the outlier galaxies hint at a combination of pre-processing and cluster-specific interactions affecting their stellar and gas disks.

The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z ∼ 8

ABSTRACT We analyse the chemical properties of three z∼ 8 galaxies behind the galaxy cluster SMACS J0723.3-7327, observed as part of the Early Release Observations programme of the James Webb Space Telescope. Exploiting [O iii]λ4363 auroral line detections in NIRSpec spectra, we robustly apply the direct Te method for the very first time at such high redshift, measuring metallicities ranging from extremely metal poor (12 + log(O/H)≈ 7) to about one-third solar. We also discuss the excitation properties of these sources, and compare them with local strong-line metallicity calibrations. We find that none of the considered diagnostics match simultaneously the observed relations between metallicity and strong-line ratios for the three sources, implying that a proper re-assessment of the calibrations may be needed at these redshifts. On the mass–metallicity plane, the two galaxies at z ∼ 7.6 ($\rm log(M_*/M_{\odot }) = 8.1, 8.7$) have metallicities that are consistent with the extrapolation of the mass–metallicity relation at z∼2–3, while the least massive galaxy at z ∼ 8.5 ($\rm log(M_*/M_{\odot }) = 7.8$) shows instead a significantly lower metallicity. The three galaxies show different level of offset relative to the Fundamental Metallicity Relation, with two of them (at z∼ 7.6) being marginally consistent, while the z∼ 8.5 source deviating significantly, being probably far from the smooth equilibrium between gas flows, star formation, and metal enrichment in place at later epochs.