Tycho-Gaia Astrometric Solution Parallaxes and Proper Motions for Five Galactic Globular Clusters

Abstract

We present a pilot study of Galactic globular cluster (GC) proper motion (PM) determinations using Gaia data. We search for GC stars in the Tycho-Gaia Astrometric Solution (TGAS) catalogue from Gaia Data Release 1 (DR1), and identify five members of NGC104 (47 Tucanae), one member of NGC5272 (M3), five members of NGC6121 (M4), seven members of NGC6397, and two members of NGC6656 (M22). By taking a weighted average of member stars, fully accounting for the correlations between parameters, we estimate the parallax (and, hence, distance) and PM of the GCs. This provides a homogeneous PM study of multiple GCs based on an astrometric catalog with small and well-controlled systematic errors, and yields random PM errors similar to existing measurements. Detailed comparison to the available Hubble Space Telescope (HST) measurements generally shows excellent agreement, validating the astrometric quality of both TGAS and HST. By contrast, comparison to ground-based measurements shows that some of those must have systematic errors exceeding the random errors. Our parallax estimates have uncertainties an order of magnitude larger than previous studies, but nevertheless imply distances consistent with previous estimates. By combining our PM measurements with literature positions, distances, and radial velocities, we measure Galactocentric space motions for the clusters and find that these also agree well with previous analyses. Our analysis provides a framework for determining more accurate distances and PMs of Galactic GCs using future Gaia data releases. This will provide crucial constraints on the near end of the cosmic distance ladder and provide accurate GC orbital histories.

15 pages, 11 figures, 4 tables. Published in ApJ. Revised to match published version

References in corpus (19)

• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The Dartmouth Stellar Evolution Database
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The Radial Velocity Experiment (RAVE): Fifth Data Release
• Is the SMC Bound to the LMC? The HST Proper Motion of the SMC
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• The White Dwarf Cooling Sequence of NGC6397
• Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. I. Sample Selection, Data Reduction and NGC 7078 Results
• Estimating distances from parallaxes. II. Performance of Bayesian distance estimators on a Gaia-like catalogue
• Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular clusters. II. Kinematic profiles and maps
• Space Velocities of Southern Globular Clusters. V. A Low Galactic Latitude Sample
• First Gaia Local Group Dynamics: Magellanic Clouds Proper Motion and Rotation
• Relative distances of Omega Centauri and 47 Tucanae
• The Effect of Orbital Eccentricity on the Dynamical Evolution of Star Clusters
• Spectroscopic Signatures of Extra-Tidal Stars Around the Globular Clusters NGC 6656 (M22), NGC 3201 and NGC 1851 from RAVE
• Absolute motions of globular clusters. II. [HST astrometry and VLT radial velocities in NGC6397]
• The power of teaming up HST and Gaia: the first proper motion measurement of the distant cluster NGC 2419
• A discrete chemo-dynamical model of the giant elliptical galaxy NGC 5846: dark matter fraction, internal rotation and velocity anisotropy out to six effective radii
• The Space Motion of the Globular Cluster NGC 6397

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• Gaia and VLT astrometry of faint stars: Precision of Gaia DR1 positions and updated VLT parallaxes of ultracool dwarfs
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