Hubble Space Telescope analysis of stellar populations within the globular cluster G1 (Mayall II) in M31

Abstract

In this paper we present a multi-wavelength analysis of the complex stellar populations within the massive globular cluster Mayall II (G1), a satellite of the nearby Andromeda galaxy projected at a distance of 40 kpc. We used images collected with the Hubble Space Telescope in UV, blue and optical filters to explore the multiple stellar populations hosted by G1. The $m_{F438W}$ versus $m_{F438W}-m_{F606W}$ colour-magnitude diagram shows a significant spread of the red giant branch, that divides $\sim 1$ mag brighter than the red clump. A possible explanation is the presence of two populations with different iron abundance or different C+N+O content, or different helium content, or a combination of the three causes. A similar red giant branch split is observed also for the Galactic globular cluster NGC6388. Our multi-wavelength analysis gives also the definitive proof that G1 hosts stars located on an extended blue horizontal branch. The horizontal branch of G1 exhibits similar morphology as those of NGC6388 and NGC6441, which host stellar populations with extreme helium abundance (Y>0.33). As a consequence, we suggest that G1 may also exhibit large star-to-star helium variations.

13 pages, 9 figures (2 at low resolution), 2 tables. Accepted for publication in MNRAS on March 1, 2019

References in corpus (20)

• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• 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
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Looking outside the Galaxy: the discovery of chemical anomalies in 3 old Large Magellanic Cloud clusters
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• Reaching the End of the White Dwarf Cooling Sequence in NGC 6791
• The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441: new insights from UV observations
• The Search for Multiple Populations in Magellanic Cloud Clusters II: The Detection of Multiple Populations in Three Intermediate-Age SMC Clusters
• Multiple populations in the old and massive Small Magellanic Cloud globular cluster NGC121
• Nitrogen abundances and multiple stellar populations in the globular clusters of the Fornax dSph
• Na-O Anticorrelation and HB. VI. The chemical composition of the peculiar bulge globular cluster NGC 6388
• Multiple stellar populations in Magellanic Cloud clusters. V. The split main sequence of the young cluster NGC1866
• The Search for Multiple Populations in Magellanic Cloud Clusters I: Two Stellar Populations in the Small Magellanic Cloud Globular Cluster NGC 121
• A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
• Dissecting the Extended Main Sequence Turn-off of the Young Star Cluster NGC1850
• Observing multiple stellar populations with FORS2@VLT - Main sequence photometry in outer regions of NGC 6752, NGC 6397, and NGC 6121 (M 4)
• Structural Parameters of Mayall II = G1 in M31
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters -- XI. The horizontal branch in NGC\,6388 and NGC\,6441

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• The Physics of Star Cluster Formation and Evolution
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• The role of rotation on the formation of second generation stars in globular clusters
• Confirmation of a metallicity spread amongst first population stars in globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIV. Differences in internal kinematics of multiple stellar populations
• High-precision abundances of first population stars in NGC 2808: confirmation of a metallicity spread
• Photometric characterization of multiple populations in star clusters: The impact of the first dredge-up
• Second generation star formation in globular clusters of different masses
• JWST unveils the brown dwarf sequence of 47 Tucanae
• The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy
• Hubble Space Telescope imaging of the extremely metal-poor globular cluster EXT8 in Messier 31
• Metallicities of Outer Halo M31 Globular Clusters from Integrated Light Calcium-II Triplet Spectroscopy
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXII. Relative ages of multiple populations in five Globular Clusters