The dynamics of the globular cluster NGC3201 out to the Jacobi radius

Abstract

As part of a chemo-dynamical survey of five nearby globular clusters with 2dF/AAOmega on the AAT, we have obtained kinematic information for the globular cluster NGC3201. Our new observations confirm the presence of a significant velocity gradient across the cluster which can almost entirely be explained by the high proper motion of the cluster. After subtracting the contribution of this perspective rotation, we found a remaining rotation signal with an amplitude of $\sim 1km/s$ around a different axis to what we expect from the tidal tails and the potential escapers, suggesting that this rotation is internal and can be a remnant of its formation process. At the outer part, we found a rotational signal that is likely a result from potential escapers. The proper motion dispersion at large radii reported by Bianchini et al. has previously been attributed to dark matter. Here we show that the LOS dispersion between 0.5-1 Jacobi radius is lower, yet above the predictions from an N-body model of NGC3201 that we ran for this study. Based on the simulation, we find that potential escapers cannot fully explain the observed velocity dispersion. We also estimate the effect on the velocity dispersion of different amounts of stellar-mass black holes and unbound stars from the tidal tails with varying escape rates and find that these effects cannot explain the difference between the LOS dispersion and the N-body model. Given the recent discovery of tidal tail stars at large distances from the cluster, a dark matter halo is an unlikely explanation. We show that the effect of binary stars, which is not included in the N-body model, is important and can explain part of the difference in dispersion. We speculate that the remaining difference must be the result of effects not included in the N-body model, such as initial cluster rotation, velocity anisotropy and Galactic substructure.

14 pages, 13 figures, accepted by MNRAS

References in corpus (27)

• galpy: A Python Library for Galactic Dynamics
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• A stellar census in globular clusters with MUSE: The contribution of rotation to cluster dynamics studied with 200 000 stars
• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• Black holes and core expansion in massive star clusters
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular clusters. II. Kinematic profiles and maps
• Generation of mock tidal streams
• A New Catalog of Globular Clusters in the Milky Way
• The eye of Gaia on globular clusters kinematics: internal rotation
• Measuring Consistent Masses for 25 Milky Way Globular Clusters
• The effect of stellar-mass black holes on the structural evolution of massive star clusters
• Globular cluster number density profiles using Gaia DR2
• A stellar-mass black hole population in the globular cluster NGC 6101?
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• The halo+cluster system of the Galactic globular cluster NGC1851
• Multi-Object Spectroscopy Field Configuration by Simulated Annealing
• High mass-to-light ratios of UCDs - Evidence for dark matter ?
• Spectroscopic Signatures of Extra-Tidal Stars Around the Globular Clusters NGC 6656 (M22), NGC 3201 and NGC 1851 from RAVE
• Mass models of NGC 6624 without an intermediate-mass black hole
• Stellar envelopes of globular clusters embedded in dark mini-haloes
• Using globular clusters to test gravity in the weak acceleration regime: NGC 7099
• Exploring the outskirts of globular clusters: the peculiar kinematics of NGC 3201
• The complex kinematics of rotating star clusters in a tidal field
• Spherical models of star clusters with potential escapers
• The survival of star clusters with black hole subsystems
• An Approximate Analytic Model of a Star Cluster with Potential Escapers

Cited by in corpus (19)

• Evidence for a bottom-light initial mass function in massive star clusters
• A Wide-Field View on Multiple Stellar Populations in 28 Milky Way Globular Clusters
• Stellar graveyards: Clustering of compact objects in globular clusters NGC 3201 and NGC 6397
• On the Use of Field RR Lyrae as Galactic Probes. V. Optical and radial velocity curve templates
• Early dynamical evolution of rotating star clusters in a tidal field
• Detecting Axion Dark Matter through the Radio Signal from Omega Centauri
• Early dynamics and violent relaxation of multi-mass rotating star clusters
• Testing for Dark Matter in the Outskirts of Globular Clusters
• Could compact stars in globular clusters constrain dark matter?
• The Kinematics of 30 Milky Way Globular Clusters and the Multiple Stellar Populations within
• The Dark Matter Halo of M54
• Absence of obvious tidal tails around the globular cluster NGC 6397
• Dynamics in the outskirts of four Milky Way globular clusters: it's the tides that dominate
• DECam photometry reveals extra-tidal stars around the Milky Way globular cluster NGC 6864 (M75)
• On the physical size of the Milky Way globular cluster NGC 7089 (M 2)
• Direct N-body simulations of NGC 6397 and its tidal tails
• Investigating Dynamical Properties of Globular Clusters through a Family of Lowered Isothermal Models
• Predicting Images for the Dynamics Of stellar Clusters (π-DOC): a deep learning framework to predict mass, distance and age of globular clusters
• A search for stellar structures around nine outer halo globular clusters in the Milky Way