A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters

Abstract: We have determined masses, stellar mass functions and structural parameters of 112 Milky Way globular clusters by fitting a large set of N-body simulations to their velocity dispersion and surface density profiles. The velocity dispersion profiles were calculated based on a combination of more than 15,000 high-precision radial velocities which we derived from archival ESO/VLT and Keck spectra together with ~20,000 published radial velocities from the literature. Our fits also include the stellar mass functions of the globular clusters, which are available for 47 clusters in our sample, allowing us to self-consistently take the effects of mass segregation and ongoing cluster dissolution into account. We confirm the strong correlation between the global mass functions of globular clusters and their relaxation times recently found by Sollima & Baumgardt (2017). We also find a correlation of the escape velocity from the centre of a globular cluster and the fraction of first generation stars (FG) in the cluster recently derived for 57 globular clusters by Milone et al. (2017), but no correlation between the FG star fraction and the global mass function of a globular cluster. This could indicate that the ability of a globular cluster to keep the wind ejecta from the polluting star(s) is the crucial parameter determining the presence and fraction of second generation stars and not its later dynamical mass loss.

• The paper provides a comprehensive catalogue of masses, structural parameters, and velocity dispersion profiles for 112 clusters using extensive kinematic data and N-body simulations.
• The study verifies a correlation between global mass functions, relaxation times, and central escape velocities, emphasizing the influence of initial conditions on stellar retention.
• The integration of high-precision data from ESO/VLT, Keck, and literature establishes a robust framework for understanding the dynamic evolution of Milky Way globular clusters.

Analysis of Milky Way Globular Clusters: Masses, Structure, and Dynamics

This paper presents a comprehensive study of the masses, structural parameters, and velocity dispersion profiles of 112 Milky Way globular clusters. The authors harness a wealth of kinematic data, aggregating over 15,000 high-precision radial velocities from archival sources such as ESO/VLT and Keck spectra, alongside approximately 20,000 velocities reported in existing literature. Through fitting a series of $N$-body simulations to these profiles, they derive important insights into the clusters' dynamic states.

The methodology hinges on employing $N$-body simulations, a robust approach for modeling gravitational dynamics within globular clusters. These simulations are calibrated against the empirical velocity dispersion and surface density profiles. Furthermore, the paper enhances the analysis by incorporating the stellar mass functions for nearly half of the cluster samples, allowing for a nuanced evaluation that accounts for mass segregation and potential ongoing cluster dissolution.

Key findings include the confirmation of a correlation between global mass functions and relaxation times, consistent with prior studies by Sollima and Baumgardt (2017). A notable correlation between the escape velocity at cluster centers and the fraction of first-generation (FG) stars is identified; however, the absence of a correlation between FG star fraction and global mass function suggests that a cluster's initial conditions, rather than its dynamical evolution, may principally dictate its ability to retain stellar ejecta.

The paper systematically tests these insights against empirical data, highlighting clusters such as 47 Tuc and M15, where the $N$-body models fit observed surface density and velocity dispersion profiles excellently. The correlation studies suggest dynamically evolving mass functions influenced by Galactic tidal fields and relaxation processes, leading to observable variability across clusters in the Milky Way.

Significantly, the research underscores that the central escape velocity is a pivotal factor in determining the quantity of second-generation stars, aligning with theories positing that the retention of stellar winds is crucial to enriching clusters with second-generation stars. This finding supports a scenario where initial conditions play a pivotal role in the observed chemical heterogeneity, influencing theories related to star formation and early stellar evolution.

In terms of practical implications, this work enriches our understanding of the dynamic behaviors governing globular clusters, offering a methodologically sound framework that integrates observational data with advanced simulation models. Theoretically, it supports a pivotal discussion concerning the initial mass distribution's role in shaping a globular cluster's evolutionary pathway, guiding future studies to expand upon these conceptual foundations.

These findings provide various avenues for future exploration. Increasing the resolution and scope of $N$-body simulations could enhance our understanding of the dynamical processes shaping these ancient stellar systems. Additionally, incorporating further datasets, such as proper motion data from space observatories like Gaia, may refine our comprehension of the internal dynamics of globular clusters. This paper presents a solid technical and analytical foundation upon which the field can build, inviting further investigation into the myriad factors influencing globular cluster evolution within diverse galactic environments.