Using Gaia for studying Milky Way star clusters

Abstract

We review the implications of the Gaia Data Release 2 catalogue for studying the dynamics of Milky Way globular clusters, focusing on two separate topics. The first one is the analysis of the full 6-dimensional phase-space distribution of the entire population of Milky Way globular clusters: their mean proper motions (PM) can be measured with an exquisite precision (down to 0.05 mas/yr, including systematic errors). Using these data, and a suitable ansatz for the steady-state distribution function (DF) of the cluster population, we then determine simultaneously the best-fit parameters of this DF and the total Milky Way potential. We also discuss possible correlated structures in the space of integrals of motion. The second topic addresses the internal dynamics of a few dozen of the closest and richest globular clusters, again using the Gaia PM to measure the velocity dispersion and internal rotation, with a proper treatment of spatially correlated systematic errors. Clear rotation signatures are detected in 10 clusters, and a few more show weaker signatures at a level >=0.05$ mas/yr. PM dispersion profiles can be reliably measured down to 0.1 mas/yr, and agree well with the line-of-sight velocity dispersion profiles from the literature.

arXiv commentProceedings of the IAU symposium 351 (MODEST-19)

References in corpus (15)

• galpy: A Python Library for Galactic Dynamics
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• The mass distribution and gravitational potential of the Milky Way
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• Mean proper motions, space orbits and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data
• Proper motions and dynamics of the Milky Way globular cluster system from Gaia DR2
• Assessing the Milky Way Satellites Associated with the Sagittarius Dwarf Spheroidal Galaxy
• The Sausage Globular Clusters
• Evidence for an Intermediate-Mass Milky Way from Gaia DR2 Halo Globular Cluster Motions
• Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular clusters. II. Kinematic profiles and maps
• The internal rotation of globular clusters revealed by Gaia DR2
• The eye of Gaia on globular clusters kinematics: internal rotation
• The cumulative mass profile of the Milky Way as determined by globular cluster kinematics from Gaia DR2
• Systematic errors in Gaia DR2 astrometry and their impact on measurements of internal kinematics of star clusters
• The orbital anisotropy profiles of nearby globular clusters from Gaia Data Release 2