HST astrometry in the 30 Doradus region: measuring proper motions of individual stars in the Large Magellanic Cloud

Abstract

We present measurements of positions and relative proper motions in the 30 Doradus region of the Large Magellanic Cloud (LMC). We detail the construction of a single-epoch astrometric reference frame, based on specially-designed observations obtained with the two main imaging instruments ACS/WFC and WFC3/UVIS onboard the Hubble Space Telescope (HST). Internal comparisons indicate a sub milli-arc-second (mas) precision in the positions and the presence of semi-periodic systematics with a mean amplitude of ~0.8 mas. We combined these observations with numerous archival images taken with WFPC2 and spanning 17 years. The precision of the resulting proper motions for well-measured stars around the massive cluster R 136 can be as good as ~20 microarcsec/yr, although the true accuracy of proper motions is generally lower due to the residual systematic errors. The observed proper-motion dispersion for our highest-quality measurements is ~0.1 mas/yr. Our catalog of positions and proper motions contains 86,590 stars down to V~25 and over a total area of ~70 square arcmin. We examined the proper motions of 105 relatively bright stars and identified a total of 6 candidate runaway stars. We are able to tentatively confirm the runaway status of star VFTS 285, consistent with the findings from line-of-sight velocities, and to show that this star has likely been ejected from R 136. This study demonstrates that with HST it is now possible to reliably measure proper motions of individual stars in the nearest dwarf galaxies such as the LMC.

33 pages, 19 figures (1 in low-res), 3 tables. Accepted for publication in AJ

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Cited by in corpus (11)

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• Hubble Tarantula Treasury Project. III. Photometric Catalog and Resulting Constraints on the Progression of Star Formation in the 30 Doradus Region
• The VLT-FLAMES Tarantula Survey XXVI: Properties of the O-dwarf population in 30 Doradus
• Deciphering the Kinematic Structure of the Small Magellanic Cloud through its Red Giant Population
• Gaia and HST astrometry of the very massive $\sim$150 $M_{\odot }$ candidate runaway star VFTS682
• HST astrometry in the 30 Doradus region: II. Runaway stars from new proper motions in the Large Magellanic Cloud
• HST astrometry in the Orion Nebula Cluster: census of low-mass runaways
• Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars:Candidate hypervelocity star discovery, and the nature of R71
• Faint Stars in a Faint Galaxy: II. The Low Mass Stellar Initial Mass Function of the Boötes I Ultrafaint Dwarf Spheroidal Galaxy
• A clustered origin for isolated massive stars
• Extreme adaptive optics astrometry of R136. Searching for high proper motion stars