A Wide View of the Galactic Globular Cluster NGC 2808: Red Giant and Horizontal Branch Star Spatial Distributions

Abstract

Wide-field and deep DECam multi-band photometry, combined with HST data for the core of the Galactic globular cluster NGC 2808, allowed us to study the distribution of various stellar sub-populations and stars in different evolutionary phases out to the cluster tidal radius. We used the C_ugi = (u-g)-(g-i) index to identify three chemically distinct sub-populations along the red giant branch and compared their spatial distributions. The most light-element enriched sub-population (P3) is more centrally concentrated; however, it shows a more extended distribution in the external regions of the cluster compared to the primordial (P1) and intermediate (P2) composition populations. Furthermore, the P3 sub-population centroid is off-center relative to those of the P1 and P2 groups. We also analyzed the spatial distribution of horizontal branch stars and found that the relative fraction of red horizontal branch stars increases for radial distances larger than ~ 1.5' while that of the blue and hotter stars decreases. These new observations, combined with literature spectroscopic measurements, suggest that the red horizontal branch stars are the progeny of all the stellar sub-populations in NGC 2808, i.e. primordial and light-element enhanced, while the blue stars are possibly the result of a combination of the "hot-flasher" and the "helium-enhanced" scenarios. A similar distribution of different red giant branch sub-populations and horizontal branch stars was also found for the most massive Galactic globular cluster, omega Cen, based on combined DECam and HST data, which suggests the two may share a similar origin.

Accepted for publication in AJ; 22 pages; 16 figures; the full version of table 2 will be available in electronic form with the published version

References in corpus (27)

• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Gaia EDR3 view on Galactic globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• The updated BaSTI stellar evolution models and isochrones: II. alpha-enhanced calculations
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• Globular cluster number density profiles using Gaia DR2
• Multiple populations in globular clusters: the distinct kinematic imprints of different formation scenarios
• Dynamical Evolution of Multiple-Population Globular Clusters
• The link between chemical anomalies along the red giant branch and the horizontal branch extension in globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. X. The radial distribution of stellar populations in NGC 2808
• The Hottest Horizontal-Branch Stars in omega Centauri - Late Hot Flasher vs. Helium Enrichment
• Blanco DECam Bulge Survey (BDBS) II: Project Performance, Data Analysis, and Early Science Results
• A Helium-Carbon Correlation on the Extreme Horizontal Branch in $\omega$ Centauri
• A stellar census in globular clusters with MUSE: Multiple populations chemistry in NGC 2808
• Early dynamical evolution of rotating star clusters in a tidal field
• Light Element Discontinuities Suggest an Early Termination of Star Formation in the Globular Cluster NGC 6402 (M14)
• On the radial distribution of horizontal branch stars in ngc2808
• The not so simple stellar system Omega Cen. II. Evidence in support of a merging scenario
• HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations
• Investigation of the Globular Cluster NGC 2808 with the Ultra-Violet Imaging Telescope
• The chemical compositions of multiple stellar populations in the globular cluster NGC 2808
• New sub-grouping of multiple stellar populations in NGC 2808 based on low-resolution spectroscopy
• Robust statistical tools for identifying multiple stellar populations in globular clusters in the presence of measurement errors. A case study: NGC 2808

Cited by in corpus (3)

• Discrepancies between spectroscopy and HST photometry in tagging multiple stellar populations in 22 globular clusters
• Inconsistent metallicity spreads in first generation stars of globular clusters from high resolution spectroscopy and HST photometry
• An excess of luminous white dwarfs in the peculiar Galactic globular cluster NGC 2808