The KLEVER survey: nitrogen abundances at z ∼2 and probing the existence of a fundamental nitrogen relation

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Curti, M 
Maiolino, R 
Cirasuolo, M 

We present a comparison of the nitrogen-to-oxygen ratio (N/O) in 37 high-redshift galaxies at $z\sim$2 taken from the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey with a comparison sample of local galaxies, taken from the Sloan Digital Sky Survey (SDSS). The KLEVER sample shows only a mild enrichment in N/O of $+$0.1 dex when compared to local galaxies at a given gas-phase metallicity (O/H), but shows a depletion in N/O of $-0.36dexwhencomparedatafixedstellarmass(M*).WefindastronganticorrelationinlocalgalaxiesbetweenN/OandSFRintheM*N/Oplane,similartotheanticorrelationbetweenO/HandSFRfoundinthemassmetallicityrelation(MZR).Weusethisanticorrelationtoconstructafundamentalnitrogenrelation(FNR),analogoustothefundamentalmetallicityrelation(FMR).WefindthatKLEVERgalaxiesareconsistentwithboththeFMRandtheFNR.ThissuggeststhatthedepletionofN/Oinhighz$ galaxies when considered at a fixed M is driven by the redshift-evolution of the mass-metallicity relation in combination with a near redshift-invariant N/O-O/H relation. Furthermore, the existence of an fundamental nitrogen relation suggests that the mechanisms governing the fundamental metallicity relation must be probed by not only O/H, but also N/O, suggesting pure-pristine gas inflows are not the primary driver of the FMR, and other properties such as variations in galaxy age and star formation efficiency must be important.

galaxies: abundances, galaxies: evolution, galaxies: high-redshift
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Monthly Notices of the Royal Astronomical Society
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Oxford University Press (OUP)
STFC (2120607)