Exploring the outskirts of globular clusters: the peculiar kinematics of NGC 3201

Abstract

The outskirts of globular clusters (GCs) simultaneously retain crucial information about their formation mechanism and the properties of their host galaxy. Thanks to the advent of precision astrometry both their morphological and kinematic properties are now accessible. Here we present the first dynamical study of the outskirts of the retrograde GC NGC 3201 until twice its Jacobi radius (< 100 pc), using specifically-selected high-quality astrometric data from Gaia DR2. We report the discovery of a stellar overdensity along the South-East/North-West direction that we identify as tidal tails. The GC is characterized globally by radial anisotropy and a hint of isotropy in the outer parts, with an excess of tangential orbits around the lobes corresponding to the tidal tails, in qualitative agreement with an N-body simulation. Moreover, we measure flat velocity dispersion profiles, reaching values of $3.5\pm 0.9$ km/s until beyond the Jacobi radius. While tidal tails could contribute to such a flattening, this high velocity dispersion value is in disagreement with the expectation from the sole presence of potential escapers. To explain this puzzling observation, we discuss the possibility of an accreted origin of the GC, the presence of a dark matter halo --leftover of its formation at high redshift -- and the possible effects of non-Newtonian dynamics. Our study uncovers a new path for the study of GC formation and of the properties of the Milky Way potential in the era of precision astrometry.

arXiv comment9 pages, 4 figure, 1 table. Accepted for publication to ApJ Letters

References in corpus (55)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• Gaia Data Release 2: The astrometric solution
• Adaptive spatial binning of integral-field spectroscopic data using Voronoi tessellations
• The New Galaxy: Signatures of its Formation
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions
• Dynamical evolution of star clusters in tidal fields
• Resolved Massive Star Clusters in the Milky Way and its Satellites: Brightness Profiles and a Catalogue of Fundamental Parameters
• Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way
• A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters
• Origin of the system of globular clusters in the Milky Way
• The dynamical distance and intrinsic structure of the globular cluster omega Centauri
• Globular Clusters with Tidal Tails: Deep Two-Color Star Counts
• The Bifurcated Age-Metallicity Relation of Milky Way Globular Clusters and its Implications For the Accretion History of the Galaxy
• The Time Scale of Escape from Star Clusters
• The internal rotation of globular clusters revealed by Gaia DR2
• Do globular clusters possess Dark Matter halos? A case study in NGC 2419
• No Energy Equipartition in Globular Clusters
• STREAMFINDER I: A New Algorithm for detecting Stellar Streams
• Peculiarities in Velocity Dispersion and Surface Density Profiles of Star Clusters
• Halo globular clusters observed with AAOmega: dark matter content, metallicity and tidal heating
• The eye of Gaia on globular clusters kinematics: internal rotation
• The devil is in the tails: the role of globular cluster mass evolution on stream properties
• A novel look at energy equipartition in globular clusters
• Globular cluster number density profiles using Gaia DR2
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• A Common Origin for Globular Clusters and Ultra-faint Dwarfs in Simulations of the First Galaxies
• Velocity anisotropy in tidally limited star clusters
• The Global Kinematics of the Globular Cluster M15
• Butterfly in a Cocoon, Understanding the origin and morphology of Globular Cluster Streams: The case of GD-1
• Stellar streams as gravitational experiments II. Asymmetric tails of globular cluster streams
• Systematic errors in Gaia DR2 astrometry and their impact on measurements of internal kinematics of star clusters
• A dynamical study of Galactic globular clusters under different relaxation conditions
• The properties of energetically unbound stars in stellar clusters
• Spectroscopic Signatures of Extra-Tidal Stars Around the Globular Clusters NGC 6656 (M22), NGC 3201 and NGC 1851 from RAVE
• A wide-field photometric survey for extratidal tails around five metal-poor globular clusters in the Galactic halo
• Testing lowered isothermal models with direct N-body simulations of globular clusters
• Stellar envelopes of globular clusters embedded in dark mini-haloes
• Using globular clusters to test gravity in the weak acceleration regime: NGC 7099
• Search for Extra-Tidal RR Lyrae Stars in Milky Way Globular Clusters From Gaia DR2
• Flattened velocity dispersion profiles in Globular Clusters: Newtonian tides or modified gravity?
• The orbital anisotropy profiles of nearby globular clusters from Gaia Data Release 2
• Phase-space correlation in stellar streams of the Milky Way halo: The clash of Kshir and GD-1
• Characterization of the velocity anisotropy of accreted globular clusters
• An Approximate Analytic Model of a Star Cluster with Potential Escapers
• Using Gaia DR2 to detect extratidal structures around the Galactic globular cluster NGC362
• A flexible method to evolve collisional systems and their tidal debris in external potentials
• Distant star clusters of the Milky Way in MOND
• Kinematic fingerprint of core-collapsed globular clusters
• The Dynamical Evolution of Accreted Star Clusters in the Milky Way
• The dynamics of the outer parts of omega Centauri
• Identification of Globular Cluster Stars in RAVE data II: Extended tidal debris around NGC 3201
• Kinematics of a globular cluster with an extended profile: NGC5694
• The MOND External Field Effect on the Dynamics of the Globular Clusters: General Considerations and Application to NGC 2419

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• Predicting Images for the Dynamics Of stellar Clusters (π-DOC): a deep learning framework to predict mass, distance and age of globular clusters
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