Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN-CH-NH Photometry. VI. M3 (NGC 5272) is not a Prototypical Normal Globular Cluster

Abstract

We present Ca-CN-CH-NH photometry for the well-known globular cluster (GC) M3 (NGC 5272). We show new evidence for two M3 populations with distinctly different carbon and nitrogen abundances, seen in a sharp division between CN-weak and CN-strong red-giant branches (RGBs) in M3. The CN-strong population shows a C-N anticorrelation that is a natural consequence of the CN cycle, while the CN-weak population shows no or a weak C-N anticorrelation. Additionally, the CN-weak population exhibits an elongated spatial distribution that is likely linked to its fast rotation. Our derived metallicity reveals bimodal metallicity distributions in both populations, with $⟨$[Fe/H]$⟩\approx -$1.60 and $-$1.45, which appear to be responsible for the discrete double RGB bumps in the CN-weak and the large $W_{F275W-F814W}^{1G}$ range. From this discovery, we propose that M3 consists of two GCs, namely the C1 (23\%, $⟨$[Fe/H]$⟩\approx -1.60$) and C2 (77\%, $⟨$[Fe/H]$⟩\approx -1.45$), each of which has its own C-N anticorrelation and structural and kinematical property, which is a strong indication of independent systems in M3. The fractions of the CN-weak population for both the C1 and C2 are high compared to Galactic GCs but they are in good agreement with GCs in Magellanic Clouds. It is believed that M3 is a merger remnant of the two GCs, most likely in a dwarf galaxy environment, and accreted to our Galaxy later in time. This is consistent with recent proposals of an ex-situ origin of M3.

Accepted for publication in the Astrophysical Journal (33 pages, 31 figures)

References in corpus (21)

• The Dartmouth Stellar Evolution Database
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Thermohaline mixing: A physical mechanism governing the photospheric composition of low-mass giants
• What is a globular cluster? An observational perspective
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• Looking outside the Galaxy: the discovery of chemical anomalies in 3 old Large Magellanic Cloud clusters
• VLT/UVES Spectroscopy of Individual Stars in Three Globular Clusters in the Fornax Dwarf Spheroidal Galaxy
• Nitrogen abundances in giant stars of the globular cluster NGC 6752
• 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
• Central rotations of Milky Way Globular Clusters
• Multiple Stellar Populations of Globular Clusters from Homogenous Ca by Photometry I. M22 (NGC 6656)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XII. The RGB Bumps of multiple stellar populations
• Multiple stellar populations of globular clusters from homogeneous Ca-Cn photometry. II. M5 (NGC 5904) and a new filter system
• Is helium the key parameter in the extended color spread of the first generation stars in M3?
• Multiple stellar populations of globular clusters from homogeneous Ca--CN photometry. III. NGC 6752
• Five Stellar Populations in M22 (NGC 6656)
• 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
• Structure of our Galactic Bulge from CN Measurements

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• Kinematic differences between multiple populations in Galactic globular clusters
• Calibration of the convective parameters in stellar pulsation hydrocodes
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• Evidence for C and Mg variations in the GD-1 stellar stream
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• M92 (NGC~6341) Is a Metal-Complex Globular Cluster with an Atypical Primordial Population
• Multi-wavelength Photometric Study of RR Lyrae Variables in the Globular Cluster NGC 5272 (Messier 3)
• A Comparative Study Between M30 and M92 : M92 Is A Merger Remnant With A Large Helium Enhancement
• Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters
• A search for photometric variability towards the globular cluster M3 with the TWenty Inch Survey Telescope