New Subgrouping of Multiple Stellar Populations in NGC 2808 Based on Low-resolution Spectroscopy

We performed low-resolution spectroscopy for the red giant branch stars in an intriguing globular cluster (GC) NGC 2808, which hosts subpopulations with extreme helium and light-element abundances. In order to trace N, C, Ca abundance differences among subpopulations, we measured CN, CH, ii H&K spectral indices, respectively. identified four (G1, G2, G3, G4) from CN CH strength, CN-weak/CH-strong G1, CN-intermediate/CH-strong CN-strong/CH-intermediate CN-strong/CH-weak G4. Compared [Na/O] high-resolution spectroscopy, show that index can more clearly separate G1 G2. Since traces N a GC, it implies G2 would larger difference [N/Fe] compared [Na/Fe], as predicted by chemical evolution models. Later generation G3 G4, however, are better separated spectroscopy. also found G4 shows stronger line strength of but suspect this be result unusually strong He enhancement and/or Mg depletion GC. This work illustrates combining low- spectroscopic studies improve separation GCs.