Structure and Internal Kinematics of Nine Inner Milky Way Globular Clusters

Abstract

This study constitutes part of a larger effort aimed at better characterizing the Galactic globular clusters (GGCs) located towards the inner Milky Way bulge and disk. Here, we focus on internal kinematics of nine GGCs, obtained from space-based imaging over time baselines of $>$9 years. We exploit multiple avenues to assess the dynamical state of the target GGCs, constructing radial profiles of projected stellar density, proper motion dispersion, and anisotropy. We posit that two-thirds (6/9) of our target GGCs are in an advanced dynamical state, and are close to (or have recently undergone) core collapse, supported by at least two lines of evidence: First, we find relatively steep proper motion dispersion profiles, in accord with literature values for core-collapsed GGCs. Second, we find that our sample is, in the mean, isotropic even out to their half-light radii, although one of our target clusters (NGC 6380) is tangentially anisotropic at $>$1$\sigma$ beyond its half-light radius, in accord with theoretical predictions for clusters evolving in strong tidal fields. Our proper motion dispersion and anisotropy profiles are made publicly available.

AJ in press

References in corpus (19)

• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• Near-IR properties of 24 Globular Clusters in the Galactic Bulge
• Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. I. Sample Selection, Data Reduction and NGC 7078 Results
• Surface Brightness Profiles of Galactic Globular Clusters from Hubble Space Telescope Images
• Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular clusters. II. Kinematic profiles and maps
• Globular cluster number density profiles using Gaia DR2
• Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. V. The rapid rotation of 47 Tuc traced and modeled in three dimensions
• Kinematical fingerprints of star cluster early dynamical evolution
• Variable stars in the VVV globular clusters. I. 2MASS-GC02 and Terzan10
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XVIII. Proper-motion kinematics of multiple stellar populations in the core regions of NGC 6352
• A kinematic view of NGC 1261: structural parameters, internal dispersion, absolute proper motion and Blue Straggler Stars
• Digging for relics of the past: the ancient and obscured bulge globular cluster NGC6256
• Star density profiles of six old star clusters in the Large Magellanic Cloud
• Characterization of the velocity anisotropy of accreted globular clusters
• Deep HST Imaging in 47 Tucanae: A Global Dynamical Model
• The WAGGS project -- III. Discrepant mass-to-light ratios of Galactic globular clusters at high metallicity
• A simple two-component description of energy equipartition and mass segregation for anisotropic globular clusters
• Correlation Between Mass Segregation and Structural Concentration in Relaxed Stellar Clusters

Cited by in corpus (14)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIII. Proper-motion catalogs and internal kinematics
• Evidence for a bottom-light initial mass function in massive star clusters
• Discovery of a double sequence of blue straggler stars in the core-collapsed globular cluster NGC 6256
• APOGEE discovery of a chemically atypical star disrupted from NGC 6723 and captured by the Milky Way bulge
• New insights into star cluster evolution towards energy equipartition
• Empirical measurement of the dynamical ages of three globular clusters and some considerations on the use of the dynamical clock
• APOGEE-2S Discovery of Light- and Heavy-Element Abundance Correlations in the Bulge Globular Cluster NGC 6380
• Early dynamics and violent relaxation of multi-mass rotating star clusters
• Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge
• Dynamics of star clusters with tangentially anisotropic velocity distribution
• Searching for new observational signatures of the dynamical evolution of star clusters
• Self-consistent dynamical models with a finite extent -- II. Radially truncated models
• Hierarchical Bayesian Inference of Globular Cluster Properties