New sub-grouping of multiple stellar populations in NGC 2808 based on low-resolution spectroscopy

Abstract

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

arXiv commentAccepted for publication in AJ

References in corpus (74)

• Galactic Chemical Evolution: Hydrogen Through Zinc
• Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• A Triple Main Sequence in the Globular Cluster NGC 2808
• Multiple Stellar Populations in Globular Clusters
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Na-O Anticorrelation and HB. VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra
• Massive binaries as the source of abundance anomalies in globular clusters
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139)
• The giant, horizontal and asymptotic branches of galactic globular clusters. I. The catalog, photometric observables and features
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. V. Constraints on Formation Scenarios
• Super-Massive Stars as a Source of Abundance Anomalies of Proton-Capture Elements in Globular Clusters
• Early Disc Accretion as the Origin of Abundance Anomalies in Globular Clusters
• The early evolution of Globular Clusters: the case of NGC 2808
• Multiple stellar populations in 47 Tucanae
• Abundance patterns of multiple populations in Globular Clusters: a chemical evolution model based on yields from AGB ejecta
• Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters
• Concurrent formation of supermassive stars and globular clusters: implications for early self-enrichment
• Super Helium-Rich Population and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. III. A quintuple stellar population in NGC2808
• A unique model for the variety of multiple populations formation(s) in globular clusters: a temporal sequence
• Na-O Anticorrelation And HB I. The Na-O anticorrelation in NGC 2808
• Enrichment by supernovae in globular clusters with multiple populations
• News from the Galactic suburbia: the chemical composition of the remote globular cluster NGC 2419
• Helium enhanced stars and multiple populations along the horizontal branch of NGC2808: direct spectroscopic measurements
• Superbubble dynamics in globular cluster infancy II. Consequences for secondary star formation in the context of self-enrichment via fast rotating massive stars
• The influence of residual gas expulsion on the evolution of the Galactic globular cluster system and the origin of the Population II halo
• Mining SDSS in search of Multiple Populations in Globular Clusters
• Abundances in red giant stars of NGC 2808 and correlations between chemical anomalies and global parameters in globular clusters
• Remarks on statistical errors in equivalent widths
• CN abundance variations on the main sequence of 47 Tuc
• Five groups of red giants with distinct chemical composition in the globular cluster NGC 2808
• The Presence of Two Distinct Red Giant Branches in the Globular Cluster NGC 1851
• The peculiar Horizontal Branch of NGC 2808
• Measuring helium abundance difference in giants of NGC 2808
• Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters. I. CH and CN band strength variations
• NGC 2419 -- Another Remnant of Accretion by the Milky Way
• Oxygen and Sodium Abundances in M13 (NGC 6205) Giants: Linking Globular Cluster Formation Scenarios, Deep Mixing, and Post-RGB Evolution
• The Na-O anticorrelation in horizontal branch stars. I. NGC 2808
• Super AGB and AGB evolution and the chemical inventory in NGC 2419
• The HST Large Program on Omega Centauri. I. Multiple stellar populations at the bottom of the main sequence probed in NIR-Optical
• The Spectra of Main Sequence Stars in Galactic Globular Clusters II. CH and CN Bands in M71
• The Milky Way without X: An alternative interpretation of the double red clump in the Galactic bulge
• Potassium: a new actor on the globular cluster chemical evolution stage. The case of NGC 2808
• Probing the IGM/Galaxy Connection Toward PKS0405-123 III: The Galaxy Survey and Correlations with OVI Absorbers
• A Survey of CN and CH Variations in Galactic Globular Clusters from SDSS Spectroscopy
• Multiple Stellar Populations of Globular Clusters from Homogenous Ca by Photometry I. M22 (NGC 6656)
• Detailed Chemical Abundances in NGC 5824: Another Metal-Poor Globular Cluster with Internal Heavy Element Abundance Variations
• Gas expulsion vs gas retention: what process dominates in young massive clusters?
• The Gradients in the 47 Tuc Red Giant Branch Bump and Horizontal Branch are Consistent With a Centrally-Concentrated, Helium-Enriched Second Stellar Generation
• Three discrete groups with homogeneous chemistry along the red giant branch in the globular cluster NGC 2808
• Aluminium abundances in five discrete stellar populations of the globular cluster NGC 2808
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. X. The radial distribution of stellar populations in NGC 2808
• The Peculiar Radial Distribution of Multiple Populations in the massive globular cluster M80
• NGC 5824: a luminous outer halo globular cluster with an intrinsic abundance spread
• Star-to-star Na and O abundance variations along the red giant branch in NGC 2808
• Low-resolution Spectroscopy for the Globular Clusters with Signs of Supernova Enrichment: M22, NGC 1851 and NGC 288
• Explaining the multiple populations in globular clusters by multiple episodes of star formation and enrichment without gas expulsion from massive star feedback
• A stellar census in globular clusters with MUSE -- Extending the CaT-metallicity relation below the horizontal branch and applying it to multiple populations
• Proton capture elements in the globular cluster NGC 2808 I. First detection of large variations in Sodium abundances along the Red Giant Branch
• The chemical composition of NGC5824, a globular cluster without iron spread but with an extreme Mg-Al anticorrelation
• A stellar census in globular clusters with MUSE: Multiple populations chemistry in NGC 2808
• A broad perspective on multiple abundance populations in the globular cluster NGC 1851
• Reversed radial distribution trend of subpopulations in the globular clusters NGC 362 and NGC 6723
• Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters
• The Pattern of CN, O, and Na Inhomogeneities on the Red Giant Branch of Messier 5
• Assembling the Milky Way bulge from globular clusters: Evidence from the double red clump
• The CN-CH positive correlation in the globular cluster NGC 5286
• Photometric characterization of multiple populations in star clusters: The impact of the first dredge-up
• Identifying Multiple Populations in M71 Using CN
• Evidence for Enrichment by Supernovae in the Globular Cluster NGC 6273

Cited by in corpus (3)

• The chemical compositions of multiple stellar populations in the globular cluster NGC 2808
• A Wide View of the Galactic Globular Cluster NGC 2808: Red Giant and Horizontal Branch Star Spatial Distributions
• Robust statistical tools for identifying multiple stellar populations in globular clusters in the presence of measurement errors. A case study: NGC 2808