Hubble Space Telescope reveals multiple Sub-Giant Branch in eight Globular Clusters

Abstract

In the last few years many globular clusters (GCs) have revealed complex color-magnitude diagrams, with the presence of multiple main sequences (MSs), broaden or multiple sub-giant branches (SGBs) and MS turn offs, and broad or split red giant branches (RGBs). After a careful correction for differential reddening, high accuracy photometry with the Hubble Space Telescope presented in this paper reveals a broadened or even split SGB in five additional Milky Way GCs: NGC 362, NGC 5286, NGC 6656, NGC 6715, and NGC 7089. In addition, we confirm (with new and archival HST data) the presence of a split SGB in 47Tuc, NGC 1851, and NGC 6388. The fraction of faint SGB stars with respect to the entire SGB population varies from one cluster to another and ranges from $\sim$0.03 for NGC 362 to ~0.50 for NGC 6715. The average magnitude difference between the bright SGB and the faint SGB is almost the same at different wavelengths. This peculiarity is consistent with the presence of two groups of stars with either an age difference of about 1-2 Gyrs, or a significant difference in their overall C+N+O content.

47 pages, 26 figures, accepted for publication in ApJ

References in corpus (41)

• The Photometric Performance and Calibration of the HST Advanced Camera For Surveys
• A Triple Main Sequence in the Globular Cluster NGC 2808
• Omega Centauri: The Population Puzzle Goes Deeper
• The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• The ACS Survey of Galactic Globular Clusters. XII. Photometric Binaries along the Main-Sequence
• Metallicities on the Double Main Sequence of omega Centauri Imply Large Helium Enhancement
• An ACS Survey of Globular Clusters V: Star Catalog for Each Cluster
• 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
• Toward High-Precision Astrometry with WFPC2. I. Deriving an Accurate PSF
• A helium spread among the main sequence stars in NGC 2808
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• Multiple stellar populations in 47 Tucanae
• New Limits on an Intermediate Mass Black Hole in Omega Centauri: I. Hubble Space Telescope Photometry and Proper Motions
• Abundances in Stars from the Red Giant Branch Tip to Near the Main Sequence Turn Off in M71: III. Abundance Ratios
• New evidence for the complex struscture of the RGB of Omega Cen
• Astrometry and photometry with HST WFC3. II. Improved geometric-distortion corrections for 10 filters of the UVIS channel
• Transforming observational data and theoretical isochrones into the ACS/WFC Vega-mag system
• HST Proper Motions and Stellar Dynamics in the Core of the Globular Cluster 47 Tucanae
• Multiple stellar populations in three rich Large Magellanic Cloud star clusters
• 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
• Enrichment by supernovae in globular clusters with multiple populations
• Ground-Based CCD Astrometry with Wide Field Imagers. I. [Observations just a few years apart allow decontamination of field objects from members in two Globular clusters.]
• Nitrogen abundances in giant stars of the globular cluster NGC 6752
• Mixed Populations in Globular Clusters: Et Tu, 47 Tuc?
• Sodium-Oxygen anticorrelation among Horizontal Branch Stars in the Globular Cluster M4
• New HST WFC3/UVIS observations augment the stellar-population complexity of omega Centauri
• Multiple stellar populations in the Galactic globular cluster NGC 6752
• A Double Main Sequence in the Globular Cluster NGC 6397
• Detailed abundances of Red Giants in the Globular Cluster NGC~1851: C+N+O and the Origin of Multiple Populations
• The C+N+O abundances and the splitting of the subgiant branch in the Globular Cluster NGC 1851
• Tracing the evolution of NGC6397 through the chemical composition of its stellar populations
• Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. III. Padova results
• The double sub-giant branch of NGC 6656 (M22): a chemical characterization
• The Puzzling White Dwarf Cooling Sequence in NGC6791: A Simple Solution
• The Radial Distribution of the Two Stellar Populations in NGC 1851
• The helium spread in the Globular cluster 47 Tuc
• MCAO near-IR photometry of the Globular Cluster NGC 6388: MAD observations in crowded fields
• C and N abundances of MS and SGB stars in NGC 1851

Cited by in corpus (122)

• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Multiple Stellar Populations in Globular Clusters
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The Ages of 55 Globular Clusters as Determined Using an Improved delta V_TO^HB Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Hot subluminous stars
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models
• A WFC3/HST view of the three stellar populations in the Globular Cluster NGC6752
• A unique model for the variety of multiple populations formation(s) in globular clusters: a temporal sequence
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• The SUMO project I. A survey of multiple populations in globular clusters
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• Ruprecht 106: the first single population Globular Cluster?
• Star clusters near and far; tracing star formation across cosmic time
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• The Physics of Star Cluster Formation and Evolution
• Global and non-global parameters of horizontal branch morphology of globular clusters
• Constraining Globular Cluster Formation Through Studies of Young Massive Clusters: I. A lack of ongoing star formation within young clusters
• Multiple populations in globular clusters and their parent galaxies
• Hubble Space Telescope Proper motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VI. Improved data reduction and internal-kinematic analysis of NGC 362
• A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)
• Discrete dynamical modelling of omega Centauri
• Multiple populations in globular clusters: the distinct kinematic imprints of different formation scenarios
• The extended Main Sequence Turn Off cluster NGC1856: rotational evolution in a coeval stellar ensemble
• Terzan 8: a Sagittarius-flavoured globular cluster
• NGC 362: another globular cluster with a split red giant branch
• The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)
• Constraining stellar population models - I. Age, metallicity, and abundance pattern compilation for Galactic globular clusters
• No Evidence for Significant Age Spreads in Young Massive LMC Clusters
• Helium and Multiple Populations in the Massive Globular Cluster NGC6266 (M62)
• The intriguing stellar populations in the globular clusters NGC 6388 and NGC 6441
• Hubble Space Telescope survey of Magellanic Cloud star clusters. Photometry and astrometry of 113 clusters and early results
• The halo+cluster system of the Galactic globular cluster NGC1851
• NLTE Chemical abundances in Galactic open and globular clusters
• Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tuc
• The formation of multiple populations in the globular cluster 47 Tuc
• Absolute Ages and Distances of 22 GCs using Monte Carlo Main-Sequence Fitting
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IV. Helium content and relative age of multiple stellar populations within NGC 6352
• The chemical composition of red giants in 47 Tucanae I: Fundamental parameters and chemical abundance patterns
• Photometric properties of stellar populations in Galactic globular clusters: the role of the Mg-Al anticorrelation
• Tails and streams around the Galactic globular clusters NGC1851, NGC1904, NGC2298 and NGC2808
• Lithium abundances in globular cluster giants: NGC 1904, NGC 2808, and NGC 362
• Space Velocities of Southern Globular Clusters VII. NGC 6397, NGC 6626 (M 28) and NGC 6656 (M 22)
• 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?
• Ground-based astrometry with wide field imagers. V. Application to near-infrared detectors: HAWK-I@VLT/ESO
• Photometry and spectroscopy of multiple populations along the AGB of NGC2808 and NGC6121 (M4)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XII. The RGB Bumps of multiple stellar populations
• Multi-wavelength Hubble Space Telescope photometry of stellar populations in NGC288
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VII. Implications from the Nearly Universal Nature of Horizontal Branch Discontinuities
• Rapidly rotating second-generation progenitors for the blue hook stars of ω Cen
• A critical look at the merger scenario to explain multiple populations and rotation in iron-complex globular clusters
• Chemical abundances in the multiple sub-giant branch of 47 Tucanae: insights on its faint sub-giant branch component
• A comprehensive chemical abundance study of the outer halo globular cluster M 75
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VIII. Preliminary Public Catalog Release
• The double RGB in M 2: C, N, Sr and Ba abundances
• Clear evidence for the presence of second-generation asymptotic giant branch stars in metal-poor Galactic globular clusters
• Controversial Age Spreads from the Main Sequence Turn-Off and Red Clump in Intermediate-Age Clusters in the LMC
• Low-resolution Spectroscopy for the Globular Clusters with Signs of Supernova Enrichment: M22, NGC 1851 and NGC 288
• NGC6362: the least massive globular cluster with chemically distinct multiple populations
• On the missing second generation AGB stars in NGC6752
• On the Interpretation of Sub-Giant Branch Morphologies of Intermediate-Age Star Clusters with Extended Main Sequence Turnoffs
• Multiple Stellar Populations in Globular Clusters with JWST: a NIRCam view of 47 Tucanae
• Mapping the differential reddening in globular clusters
• Gas expulsion vs gas retention in young stellar clusters II: effects of cooling and mass segregation
• Sodium abundances of AGB and RGB stars in Galactic globular clusters II. Analysis and results of NGC 104, NGC 6121 and NGC 6809
• The complex stellar system M 22: confirming abundance variations with high precision differential measurements
• Chemical Complexity in the Eu-enhanced Monometallic Globular Cluster NGC 5986
• Evidence for multiple populations in the massive globular cluster NGC 2419 from deep uVI LBT photometry
• Sodium abundances of AGB and RGB stars in galactic globular clusters I. Analysis and results of NGC 2808
• Gaia and Hubble unveil the kinematics of stellar populations in the Type II globular clusters ω Centauri and M 22
• The Next Generation Virgo cluster Survey (NGVS). XXV. Fiducial panchromatic colors of Virgo core globular clusters and their comparison to model predictions
• Survey of multiple populations in globular clusters among very low-mass stars
• The iron dispersion of the globular cluster M 2, revised
• Lithium abundances in globular cluster giants: NGC 6218 (M12) and NGC 5904 (M5)
• A stellar census in globular clusters with MUSE -- Extending the CaT-metallicity relation below the horizontal branch and applying it to multiple populations
• Uncovering Multiple Populations with Washington Photometry: I. The Globular Cluster NGC 1851
• The chemical composition of NGC5824, a globular cluster without iron spread but with an extreme Mg-Al anticorrelation
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters -- XI. The horizontal branch in NGC\,6388 and NGC\,6441
• Multiple Stellar Populations in Metal-Poor Globular Clusters with JWST: a NIRCam view of M92
• A stellar census in globular clusters with MUSE: Multiple populations chemistry in NGC 2808
• Mass loss law for red giant stars in simple population globular clusters
• Mergers, tidal interactions, and mass exchange in a population of disc globular clusters: II. Long-term evolution
• Globular Clusters in High-Redshift Dwarf Galaxies: A Case Study from the Local Group
• Atmospheric Parameters and Metallicities for 2191 stars in the Globular Cluster M4
• The Horizontal Branch population of NGC 1851 as revealed by the Ultra-violet Imaging Telescope (UVIT)
• UV Insights into the Complex Populations of M 87 Globular Clusters
• On the serendipitous discovery of a Li-rich giant in the globular cluster NGC 362
• Evolution of long-lived globular cluster stars. II. Sodium abundance variations on the asymptotic giant branch as a function of globular cluster age and metallicity
• The main sequences of NGC2808: constraints on the early disc accretion scenario
• A constraint on the formation timescale of the young open cluster NGC 2264: Lithium abundance of pre-main sequence stars
• Lithium and oxygen in globular cluster dwarfs and the early disc accretion scenario
• The Horizontal Branch of NGC 1851: Constraints from its RR Lyrae Variables
• Signatures of multiple stellar populations in unresolved extragalactic globular/ young massive star clusters
• When does the onset of multiple stellar populations in star clusters occur? Detection of enriched stellar populations in NGC 2121
• On the Onset of Secondary Stellar Generations in Giant Star Forming Regions and Massive Star Clusters
• Nucleosynthetic yields of Z=$10^{-5}$ intermediate-mass stars
• The colour-magnitude relation of Globular Clusters in Centaurus and Hydra - Constraints on star cluster self-enrichment with a link to massive Milky Way GCs
• A search for black hole microlensing signatures in globular cluster NGC 6656 (M 22)
• High Resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6681
• The Carina Project VII: Towards the breaking of the age-metallicity degeneracy of red giant branch stars using the c_UBI index
• The Celestial Buffet: multiple populations and globular cluster formation in dwarf galaxies
• The VMC survey XXVIII. Improved measurements of the proper motion of the Galactic globular cluster 47 Tucanae
• Investigation of the Globular Cluster NGC 2808 with the Ultra-Violet Imaging Telescope
• Chemical analysis of the Bulge Globular Cluster NGC 6553
• Red Giant Branch Bump Star Counts in Data and Stellar Models
• Synthetic horizontal branch morphology for different metallicities and ages under tidally enhanced stellar wind
• AstroSat study of the globular cluster NGC 2298: probable evolutionary scenarios of hot HB stars
• The realm of the Galactic globular clusters and the mass of their primordial clouds
• New SX Phe variables in the globular cluster NGC 288
• Measuring Dwarf Galaxy Intrinsic Abundance Scatter with Mid-resolution Spectroscopic Surveys: Calibrating APOGEE Abundance Errors
• A JWST project on 47 Tucanae: kinematics, energy equipartition and anisotropy of multiple populations
• Study of UV bright stellar populations in the globular cluster NGC 1261 using AstroSat
• The first Delta a observations of three globular clusters
• Exploring Multiple Stellar Populations in Globular Clusters with Euclid: A Theoretical Overview and Insights from NGC 6397
• A deep HST view of the open cluster NGC2158: binaries, mass functions, and M-dwarf discontinuity
• Multiple populations in the Sagittarius nuclear cluster M54 and in other anomalous globular clusters
• Multiple Populations in Low-mass Globular Clusters: Eridanus
• Self-shielding clumps in starburst clusters