Linking globular cluster structural parameters and their evolution: multiple stellar populations

Abstract

Globular clusters (GCs) are known to host multiple stellar populations showing chemical anomalies in the content of light elements. The origin of such anomalies observed in Galactic GCs is still debated. Here we analyse data compiled from the Hubble Space Telescope, ground-based surveys and Gaia DR2 and explore relationships between the structural properties of GCs and the fraction of second population (2P) stars. Given the correlations we find, we conclude that the main factor driving the formation/evolution of 2P stars is the cluster mass. The existing strong correlations between the 2P fraction and the rotational velocity and concentration parameter could derive from their correlation with the cluster mass. Furthermore, we observe that increasing cluster escape velocity corresponds to higher 2P fractions. Each of the correlations found is bimodal, with a different behaviour detected for low and high mass (or escape velocity) clusters. These correlations could be consistent with an initial formation of more centrally concentrated 2P stars in deeper cluster potentials, followed by a long-term tidal stripping of stars from clusters outskirts. The latter are dominated by the more extended distributed first population (1P) stars, and therefore stronger tidal stripping would preferentially deplete the 1P population, raising the cluster 2P fraction. This also suggests a tighter distribution of initial 2P fractions than observed today. In addition, higher escape velocities allow better retention of low-velocity material ejected from 1P stars, providing an alternative/additional origin for the observed differences and the distributions of 2P fractions amongst GCs.

18 pages, 8 figures (5 in the main text, 3 in the appendix), 7 tables (3 in the main text, 4 in the appendix). Accepted for publication in MNRAS

References in corpus (26)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• What is a globular cluster? An observational perspective
• A stellar census in globular clusters with MUSE: The contribution of rotation to cluster dynamics studied with 200 000 stars
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• The eye of Gaia on globular clusters kinematics: internal rotation
• Multiple populations in globular clusters and their parent galaxies
• The possible role of stellar mergers for the formation of multiple stellar populations in globular clusters
• The Accreted Nuclear Clusters of the Milky Way
• Multiple populations in globular clusters: the distinct kinematic imprints of different formation scenarios
• Differences in the rotational properties of multiple stellar populations in M 13: a faster rotation for the "extreme" chemical subpopulation
• The search for multiple populations in Magellanic Clouds clusters - V. Correlation between cluster age and abundance spreads
• A family picture: tracing the dynamical path of the structural properties of multiple populations in globular clusters
• Dynamical Evolution of Multiple-Population Globular Clusters
• Kinematical evolution of multiple stellar populations in star clusters
• Multiple stellar populations of globular clusters from homogeneous Ca-Cn photometry. II. M5 (NGC 5904) and a new filter system
• Four stellar populations and extreme helium variation in the massive outer-halo globular cluster NGC 2419
• Multiple stellar populations along the red Horizontal Branch and Red Clump of Globular Clusters
• Gaia and Hubble unveil the kinematics of stellar populations in the Type II globular clusters ω Centauri and M 22
• NGC2298: a globular cluster on its way to disruption
• Empirical estimates of the Na-O anti-correlation in 95 Galactic globular clusters
• The peculiar kinematics of the multiple populations in the globular cluster Messier 80 (NGC 6093)
• Multiple stellar populations of globular clusters from homogeneous Ca--CN photometry. III. NGC 6752
• The Rotation of Selected Globular Clusters and the Differential Rotation of M3 in Multiple Populations from the SDSS-IV APOGEE-2 Survey
• Different Sodium enhancements among multiple populations of Milky Way globular clusters

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