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Description
NGC 1978 is one of the youngest massive globular clusters (GCs) in the Large Magellanic Cloud, with reported photometric multiple-population (MP) signatures. We present a high-resolution near-infrared abundance analysis of 19 red giant branch-like stars in NGC 1978 using H- and K-band IGRINS spectra. Stellar parameters and abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, and Ce were derived through synthetic spectral fitting. The sample has a mean [Fe/H] = -0.49 with a scatter of 0.04 dex, indicating no large iron spread. The clearest feature is a C–N anticorrelation, while O varies only weakly, and the total C+N+O abundance remains nearly constant. This suggests redistribution among C, N, and O rather than a change in total CNO content. Na and Al are not clearly enhanced in the N-rich stars, Mg shows no obvious depletion, and Ce remains nearly uniform. These results give no strong evidence for enrichment by supernovae or asymptotic giant branch stars. We also find a tentative spatial trend in [N/C] along a preferred projected axis. Overall, NGC 1978 appears to host a mild MP-like chemical pattern mainly traced by C and N, rather than a fully developed old-GC-like MP.
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