# The structural properties of multiple populations in the dynamically young globular cluster NGC 2419

**Authors:** Silvia Onorato, Mario Cadelano, Emanuele Dalessandro, Enrico Vesperini, Barbara Lanzoni, Alessio Mucciarelli  
**arXiv:** [2307.09508](https://arxiv.org/abs/2307.09508)  
**Date:** 2023-07-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.09508v1/

## Key points

- NGC 2419 is a globular cluster with the lowest dynamical age
- Study analyzed structural and morphological properties of multiple populations (MPs) in NGC 2419
- Second population (SP) stars are more centrally concentrated than first population (FP) stars
- Observation provides insights into relative concentrations of MPs during early stages of cluster evolution
- Fraction of FP stars in NGC 2419 larger than expected based on trends in other Galactic GCs
- Proposed explanation: if NGC 2419 formed in Sagittarius dwarf galaxy and later accreted by Milky Way, reduced loss rate of FP stars due to transition to weaker tidal field
- Study contributes to understanding structural properties and evolutionary history of multiple populations within NGC 2419

## Summary

NGC 2419 is a globular cluster (GC) in the Galaxy that is believed to have the lowest dynamical age. This makes it an intriguing target for studying its multiple populations (MPs), as they have likely been minimally affected by long-term dynamical evolution effects. In a recent study, researchers conducted a detailed analysis of the structural and morphological properties of the MPs in NGC 2419 using high-resolution Hubble Space Telescope (HST) and wide-field ground-based data. The study found that the second population (SP) stars, which are thought to form in the inner regions of the first population (FP) system according to formation models, are more centrally concentrated than the FP stars. This observation provides insights into the relative concentrations of MPs during the early stages of cluster evolution driven by two-body relaxation processes. Additionally, it was discovered that the fraction of FP stars in NGC 2419 is larger than expected based on trends observed in other Galactic GCs. It is proposed that if NGC 2419 formed in the Sagittarius dwarf galaxy and was later accreted by the Milky Way, this discrepancy could be explained by its transition to a weaker tidal field as it moved closer to its current Galactocentric distance of approximately 95 kiloparsecs. This transition would result in a reduced loss rate of FP stars. Overall, this study provides valuable insights into the structural properties and evolutionary history of multiple populations within NGC 2419. The findings contribute to our understanding of how globular clusters form and evolve within galaxies.