Four faint red point sources near critical curves in JWST images of Abell S1063 are interpreted as extremely magnified AGB stars and a yellow supergiant at cosmic noon.
Tracing nitrogen enrichment across cosmic time with JWST
6 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
We present a comprehensive analysis of the nitrogen-to-oxygen (N/O) abundance ratio in a sample of ~ 660 star-forming galaxies at redshift z ~ 1-6, with a median redshift of z = 3.0, using deep JWST/NIRSpec spectroscopy. Leveraging detections of faint auroral emission lines in 92 galaxies at z>1 from both the MARTA survey and a large compilation of high-redshift literature objects, we derive direct electron temperature-based abundances for nitrogen and oxygen using rest-frame optical lines. We establish the first high-redshift calibrations of strong-line N/O diagnostics based on 'direct' abundance measurements, finding a mild evolution for the N2O2 = log([NII]6585/[OII]3727,3729) diagnostic and no clear evolution for the N2S2 = log([NII]6585/[SII]6717,6731) diagnostic compared to local realisations. We then investigate the N/O-O/H relation across cosmic time using both 'direct' abundances and strong-lines based measurements (additional 535 galaxies). We find evidence for mild but systematic nitrogen enhancement at high redshift: galaxies at z>1 exhibit N/O ratios elevated by ~0.18 dex (median offset) at fixed O/H compared to local trends, with a more pronounced enhancement at low metallicity (i.e. 12 + log(O/H) < 8.1), where the offset reaches up to ~0.4-0.5 dex. We consider several scenarios to explain the observed trends, including bursty star formation, differential metal loading, and inflows of pristine gas. Our results provide the most extensive confirmation of elevated N/O ratios at high-redshift to date based on rest-optical diagnostics and within a self-consistent frame.
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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.
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.
New stack-based strong-line calibrations from ~1500 spectra yield mass-metallicity relations at z=1-10 with decreasing metallicity toward higher redshift and no slope change, plus 50 EMPG candidates at 1-4% solar metallicity showing large scatter and opposite sSFR trends.
N/O ratios in z~3 star-forming galaxies are indistinguishable from low-redshift values over the metallicity range 12+log(O/H)=7.5-8.44.
citing papers explorer
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Other red dots: A possible GLIMPSE of normal AGB stars at Cosmic Noon through extreme lensing
Four faint red point sources near critical curves in JWST images of Abell S1063 are interpreted as extremely magnified AGB stars and a yellow supergiant at cosmic noon.
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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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JADES: the mass-metallicity relation at $z=1-10$. New calibrations, extremely metal-poor galaxies, and chemical diversity
New stack-based strong-line calibrations from ~1500 spectra yield mass-metallicity relations at z=1-10 with decreasing metallicity toward higher redshift and no slope change, plus 50 EMPG candidates at 1-4% solar metallicity showing large scatter and opposite sSFR trends.
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Nitrogen abundances in star-forming galaxies 2.2 Gyr after the Big Bang are not elevated
N/O ratios in z~3 star-forming galaxies are indistinguishable from low-redshift values over the metallicity range 12+log(O/H)=7.5-8.44.
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