LRD host galaxies show average metallicity 0.08 Z_sun with narrow stable range, challenging pristine-gas formation models while ruling out typical local AGN.
Novel $z\sim~10$ auroral line measurements extend the gradual offset of the FMR deep into the first Gyr of cosmic time
11 Pith papers cite this work. Polarity classification is still indexing.
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abstract
The mass assembly and chemical enrichment of the first galaxies provide key insights into their star-formation histories and the earliest stellar populations at cosmic dawn. Here we compile and utilize new, high-quality spectroscopic JWST/NIRSpec Prism observations from the JWST archive. We extend the wavelength coverage beyond the standard pipeline cutoff up to 5.5$\mu$m, enabling a detailed examination of the rest-frame optical emission-line properties for galaxies at $z\approx 10$. The improved calibration allows us to detect H$\beta$ and the [OIII]$\lambda\lambda 4959,5007$ doublet and resolve the auroral [OIII]$\lambda 4363$ line for the 11 galaxies in our sample ($z=9.3-10.0$) to obtain direct $T_e$-based metallicity measurements. We find that all galaxies show high ionisation fields and electron temperatures, with derived metallicities in the range $12+\log {\rm (O/H)} = 7.1 - 8.3$, consistent with previous strong-line diagnostics at high-z. We derive an empirical relation for $M_{\rm UV}$ and 12+log(O/H) at $z\approx 10$, useful for future higher-z studies, and show that the sample galaxies are `typical' star-forming galaxies though with relatively high specific star-formation rates and with evidence for bursty star formation. Combining the rest-frame optical line analysis and detailed UV to optical SED modelling, we determine the mass-metallicity relation and the fundamental-metallicity relation of the sample, pushing the redshift frontier of these measurements to $z=10$. These results, together with literature measurements, point to a gradually decreasing MZR at higher redshifts, with a break in the FMR at $z\approx 3$, decreasing to metallicities $\approx 3\times$ lower at $z=10$ than observed during the majority of cosmic time at $z=0-3$, likely caused by massive pristine gas inflows diluting the observed metal abundances during early galaxy assembly at cosmic dawn.
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UNVERDICTED 11representative citing papers
76 N/O-enhanced galaxies at 4<z<8.5 are observed shortly after starbursts, either in the WR enrichment phase within 10 Myr or the AGB phase after 30-40 Myr following outflows.
Direct detection of CO(3-2) at z=7.31 in REBELS-25 gives M_mol ~ 10^11 M_sun with f_gas ~0.95, confirming a massive molecular reservoir and showing low-J CO remains detectable in the Epoch of Reionization.
Galaxies at z~7-10 display diverse metallicity gradients often flattened by tidal interactions or feedback, and sit well below the local fundamental metallicity relation due to pristine gas accretion.
Discovery of a very metal-poor galaxy overdensity of 17 members near a possible Pop III-enriched absorber at z=5.945, with estimated minimum halo mass of log(M_h,min/M_⊙)=10.68.
COLIBRE simulations find the galaxy gas-phase MZR already in place at z≈10 with little evolution until z≈5, then shallowens at low z, with high-mass turnover set by AGN feedback and low-mass end by core-collapse supernovae.
LRDs are interpreted as high-inclination hyper-Eddington accreting SMBHs analogous to SS 433, with V-shaped SEDs, X-ray weakness, and Balmer breaks emerging from disk self-shielding geometry.
JWST auroral-line selected galaxies at high redshift show an MZR slope of 0.38 with selection biases favoring high-SFR low-metallicity systems, while stacked non-detections lie closer to the fundamental metallicity relation.
Paschen jumps in Little Red Dots indicate their continua originate from free-bound recombination emission in low-temperature nebular gas rather than thermalized or AGN components.
JWST spectra reveal that two z~7 galaxies already show near-solar iron-to-silicon ratios with no strong odd-even effect, favoring early Type Ia supernovae over pair-instability supernovae as the source of iron enrichment.
LRDs require Compton-thick gas at moderate metallicity plus high accretion rates producing weak X-rays to explain their non-detection, implying they are not chemically pristine.
citing papers explorer
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The metallicities of little red dot host galaxies: LRDs are metal poor, but not pristine
LRD host galaxies show average metallicity 0.08 Z_sun with narrow stable range, challenging pristine-gas formation models while ruling out typical local AGN.
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Diverse Histories and Common Origins of Nitrogen-enhanced JWST Galaxies
76 N/O-enhanced galaxies at 4<z<8.5 are observed shortly after starbursts, either in the WR enrichment phase within 10 Myr or the AGB phase after 30-40 Myr following outflows.
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Direct detection of cool molecular gas in a star-forming galaxy at $z=7.31$
Direct detection of CO(3-2) at z=7.31 in REBELS-25 gives M_mol ~ 10^11 M_sun with f_gas ~0.95, confirming a massive molecular reservoir and showing low-J CO remains detectable in the Epoch of Reionization.
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Metal Mayhem at $\rm z \sim 7-10$: Diversity and Evolution of Gas-Phase Metallicity Gradients
Galaxies at z~7-10 display diverse metallicity gradients often flattened by tidal interactions or feedback, and sit well below the local fundamental metallicity relation due to pristine gas accretion.
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Possible chemical signatures of first-star enrichment in a very metal-poor galaxy overdensity near the end of reionization
Discovery of a very metal-poor galaxy overdensity of 17 members near a possible Pop III-enriched absorber at z=5.945, with estimated minimum halo mass of log(M_h,min/M_⊙)=10.68.
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The evolution of the galaxy gas-phase mass-metallicity relation from $z=15$ to $z=0$ in the COLIBRE cosmological simulations
COLIBRE simulations find the galaxy gas-phase MZR already in place at z≈10 with little evolution until z≈5, then shallowens at low z, with high-mass turnover set by AGN feedback and low-mass end by core-collapse supernovae.
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Little Red Dots as Supermassive Analogs of SS 433
LRDs are interpreted as high-inclination hyper-Eddington accreting SMBHs analogous to SS 433, with V-shaped SEDs, X-ray weakness, and Balmer breaks emerging from disk self-shielding geometry.
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Shape of Direct-Method Mass-Metallicity Relation with JWST: Fast-Track Nitrogen and Helium Enrichment
JWST auroral-line selected galaxies at high redshift show an MZR slope of 0.38 with selection biases favoring high-SFR low-metallicity systems, while stacked non-detections lie closer to the fundamental metallicity relation.
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Paschen Jumps in Little Red Dots: Evidence for Nebular Continua
Paschen jumps in Little Red Dots indicate their continua originate from free-bound recombination emission in low-temperature nebular gas rather than thermalized or AGN components.
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JWST Absorption-Line Analysis of UV-Bright Galaxies at $z=7.2-10.6$: Early Chemical Enrichment Traced by C, O, Mg, Al, Si, and Fe
JWST spectra reveal that two z~7 galaxies already show near-solar iron-to-silicon ratios with no strong odd-even effect, favoring early Type Ia supernovae over pair-instability supernovae as the source of iron enrichment.
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On the quenching of LRD X-ray emission by both Compton-thick gas and high accretion rates
LRDs require Compton-thick gas at moderate metallicity plus high accretion rates producing weak X-rays to explain their non-detection, implying they are not chemically pristine.