Spectroscopy and photometry of the least-massive Type-II globular clusters: NGC1261 AND NGC6934

Abstract

Recent work has revealed two classes of Globular Clusters (GCs), dubbed Type-I and Type-II. Type-II GCs are characterized by a blue- and a red- red giant branch composed of stars with different metallicities, often coupled with distinct abundances in the slow-neutron capture elements (s-elements). Here we continue the chemical tagging of Type-II GCs by adding the two least-massive clusters of this class, NGC1261 and NGC6934. Based on both spectroscopy and photometry, we find that red stars in NGC1261 are slightly enhanced in [Fe/H] by ~0.1 dex and confirm that red stars of NGC 6934 are enhanced in iron by ~0.2 dex. Neither NGC1261 nor NGC6934 show internal variations in the s-elements, which suggests a GC mass threshold for the occurrence of s-process enrichment. We found a significant correlation between the additional Fe locked in the red stars of Type-II GCs and the present-day mass of the cluster. Nevertheless, most Type II GCs retained a small fraction of Fe produced by SNe II, lower than the 2%; NGC6273, M54 and omega Centauri are remarkable exceptions. In the appendix, we infer for the first time chemical abundances of Lanthanum, assumed as representative of the s-elements, in M54, the GC located in the nucleus of the Sagittarius dwarf galaxy. Red-sequence stars are marginally enhanced in [La/Fe] by 0.10\pm0.06 dex, in contrast with the large [La/Fe] spread of most Type II GCs. We suggest that different processes are responsible for the enrichment in iron and s-elements in Type-II GCs.

22 pages, 10 figures, submitted

References in corpus (24)

• The Dartmouth Stellar Evolution Database
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• The double Subgiant Branch of NGC 1851: the role of the CNO abundance
• An abundance analysis of bright giants in the globular cluster NGC 1851
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• A large C+N+O abundance spread in giant stars of the globular cluster NGC 1851
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIX. A Chemical Tagging of the Multiple Stellar Populations Over the Chromosome Maps
• Multiple populations in globular clusters and their parent galaxies
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• Chemical Evolution on the Scale of Clusters of Galaxies: A Conundrum?
• The halo+cluster system of the Galactic globular cluster NGC1851
• A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
• Chemical abundances along the 1G sequence of the chromosome maps: The Globular Cluster NGC 3201
• GRACES: Gemini remote access to CFHT ESPaDOnS Spectrograph through the longest astronomical fiber ever made (Experimental phase completed.)
• Light and Heavy Element Abundance Variations in the Outer Halo Globular Cluster NGC 6229
• Multiple stellar populations in Asymptotic Giant Branch stars of Galactic Globular Clusters

Cited by in corpus (18)

• N-enhancement in GN-z11: First evidence for supermassive stars nucleosynthesis in proto-globular clusters-like conditions at high redshift ?
• Evidence for a bottom-light initial mass function in massive star clusters
• The chemical composition of globular clusters in the Local Group
• APOGEE-2S Discovery of Light- and Heavy-Element Abundance Correlations in the Bulge Globular Cluster NGC 6380
• Peeking beneath the precision floor I: metallicity spreads and multiple elemental dispersions in the globular clusters NGC 288 and NGC 362
• Searching for multiple populations in star clusters using the China Space Station Telescope
• Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge
• Energy equipartition in multiple-population globular clusters
• Evidence of globular cluster abundance anomalies in the SMC intermediate-age cluster Kron 3
• Globular Cluster Intrinsic Iron Abundance Spreads: II. Protocluster Metallicities and the Age-Metallicity Relations of Milky Way Progenitors
• Metallicity of the globular cluster NGC 6388 from high resolution spectra of more than 160 giant stars
• Investigating a predicted metallicity [Fe/H] variation in the Type II Globular Cluster NGC 362
• APOGEE-2S Mg-Al anti-correlation of the Metal-Poor Globular Cluster NGC 2298
• Black Hole Scaling Relations in the Dwarf-galaxy Regime with $Gaia$-Sausage/Enceladus and $\omega$Centauri
• Neutron-Capture Element Signatures in Globular Clusters: Insights from the Gaia-ESO Survey
• The complex stellar system M 22: constraining the chemical enrichment from AGB stars using magnesium isotope ratios
• Inferring the efficiency of convective-envelope overshooting in Red Giant Branch stars
• Gravitational waves in massive Horndeski theory with a potential