A Comparative Study Between M30 and M92 : M92 Is A Merger Remnant With A Large Helium Enhancement

Abstract

We perform a comparative study of the ex--situ second--parameter pair globular clusters (GCs) M30 and M92, having similar metallicities but different horizontal branch morphologies. We obtain the similar mean primordial carbon abundances for both clusters. However, M92 shows a large dispersion in carbon due to a more extended C--N anticorrelation, while M30 exhibits a higher primordial nitrogen abundance, suggesting that they have different chemical enrichment histories. Our new results confirm our previous result that M92 is a metal--complex GC showing a bimodal metallicity distribution. We also find that the metal--rich group of stars in M92 shows a helium enhancement as large as $\Delta Y$ $\sim$ 0.05 from the red giant branch bump (RGBB) $V$ magnitudes, which can also be supported by (i) a lack of bright RGB stars, (ii) synthetic evolutionary HB population models and (iii) the more extended spatial distribution due to different degree of the diffusion process from their lower masses. We reinterpret the [Eu/Fe] measurements by other, finding that the two metallicity groups of stars in M92 have significantly different [Eu/Fe] abundances with small scatters. This strongly suggests that they formed independently out of well mixed interstellar media in different environments. We suggest that M92 is a more complex system than a normal GC, most likely a merger remnant of two GCs or a even more complex system. In Appendix, we address the problems with the recently developed color--temperature relations and the usage of broadband photometry in the populational taggings.

arXiv commentAccepted for publication in the Astrophysical Journal; 17 Figures and 5 Tables

References in corpus (45)

• Gaia Data Release 3: Summary of the content and survey properties
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• The ACS Survey of Galactic Globular Clusters. IX. Horizontal Branch Morphology and the Second Parameter Phenomenon
• What is a globular cluster? An observational perspective
• Hot Horizontal-Branch Stars: The Ubiquitous Nature of the "Jump" in Stromgren u, Low Gravities, and the Role of Radiative Levitation of Metals
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XVI. The helium abundance of multiple populations
• The updated BaSTI stellar evolution models and isochrones: II. alpha-enhanced calculations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XVII. Public Catalogue Release
• Enrichment by supernovae in globular clusters with multiple populations
• A critical investigation on the discrepancy between the observational and theoretical Red Giant luminosity function "Bump"
• Homogeneous photometry VII. Globular clusters in the Gaia era
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• Multiple populations in globular clusters and their parent galaxies
• linemake: An Atomic and Molecular Line List Generator
• PowerModelsDistribution.jl: An Open-Source Framework for Exploring Distribution Power Flow Formulations
• Effects of Helium Enrichment in Globular Clusters I.Theoretical Plane with PGPUC stellar evolution code
• Heavy Element Dispersion in the Metal-Poor Globular Cluster M92
• The eye of Gaia on globular clusters structure: tidal tails
• Formation of Second Generation Stars in Globular Clusters
• Dynamical Evolution of Multiple-Population Globular Clusters
• Multiple Stellar Populations of Globular Clusters from Homogenous Ca by Photometry I. M22 (NGC 6656)
• A Wide-Field View on Multiple Stellar Populations in 28 Milky Way Globular Clusters
• Multiple stellar populations of globular clusters from homogeneous Ca-Cn photometry. II. M5 (NGC 5904) and a new filter system
• Wide-Field CCD Photometry of the Globular Cluster M30
• The hidden past of M92: Detection and characterization of a newly formed 17° long stellar stream using the Canada-France Imaging Survey
• The helium abundance in the metal-poor globular clusters M30 and NGC6397
• Multiple populations in massive star clusters under the magnifying glass of photometry: Theory and tools
• Multiple Stellar Populations in Metal-Poor Globular Clusters with JWST: a NIRCam view of M92
• Formation of globular clusters with multiple stellar populations from massive gas clumps in high-z gas-rich dwarf galaxies
• r-process Abundance Patterns in the Globular Cluster M92
• Multiple stellar populations of globular clusters from homogeneous Ca--CN photometry. IV. Toward precision populational tagging
• Multiple Stellar Populations of Globular Clusters From Homogeneous Ca-CN-CH-NH Photometry. VII. Metal-Poor Populations in 47 Tucanae (NGC 104)
• Five Stellar Populations in M22 (NGC 6656)
• Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN-CH-NH Photometry. VI. M3 (NGC 5272) is not a Prototypical Normal Globular Cluster
• Models for Metal-Poor Stars with Different Initial Abundances of C, N, O, Mg, and Si. II. Application to the Colour-Magnitude Diagrams of the Globular Clusters 47 Tuc, NGC 6362, M5, M3, M55, and M92
• Multiple Stellar Populations of Globular Clusters from Homogeneous Ca--CN--CH Photometry. V. $c{n}_{\mathrm{JWL}}^{\prime }$ as a Surrogate $c{n}_{\mathrm{JWL}}$ Index and NGC 6723
• Formation of Multiple Populations of M5 (NGC 5904)
• The Effect of Stellar Helium Abundance on Dynamics of Multiple Populations in Globular Clusters
• M92 (NGC~6341) Is a Metal-Complex Globular Cluster with an Atypical Primordial Population
• Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters
• Uncovering Multiple Populations in NGC 7099 (M 30) using Washington Photometry

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• Discrepancies between spectroscopy and HST photometry in tagging multiple stellar populations in 22 globular clusters