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J/A+A/595/L2 Proper motions in NGC6681 globular cluster (Massari+, 2016)
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Beginning of ReadMe :J/A+A/595/L2 Proper motions in NGC6681 globular cluster (Massari+, 2016)
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HST-GeMS proper motions in the globular cluster NGC6681.
Massari D., Fiorentino G., McConnachie A., Bellini A., Tolstoy E.,
Turri P., Andersen D., Bono G., Stetson P.B., Veran J.-P.
<Astron. Astrophys. 595, L2 (2016)>
=2016A&A...595L...2M (SIMBAD/NED BibCode)
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ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Proper motions
Keywords: astrometry - proper motions - instrumentation: adaptive optics -
globular clusters: individual: NGC6681 -
dwarf galaxies: individual: dSph
Abstract:
For the first time the astrometric capabilities of the MCAO facility
GeMS with the GSAOI camera on Gemini-South are tested to quantify the
accuracy in determining stellar proper motions in the Galactic
globular cluster NGC 6681.
Proper motions from HST/ACS for a sample of its stars are already
available, and this allows us to construct a distortion-free reference
at the epoch of GeMS observations that is used to measure and correct
the temporally changing distortions for each GeMS exposure. In this
way, we are able to compare the corrected GeMS images with a
first-epoch of HST/ACS images to recover the relative proper motion of
the Sagittarius dwarf spheroidal galaxy with respect to NGC 6681. We
find this to be
(pm_alpha_cosdelta, pm_delta_)=(4.09,-3.41)mas/yr, which matches
previous HST/ACS measurements with a very good accuracy of 0.03mas/yr
and with a comparable precision (r.m.s of 0.43mas/yr). This study
successfully demonstrates that high-quality proper motions can be
measured for quite large fields of view (85arcsecx85arcsec) with
MCAO-assisted, ground-based cameras and provides a first, successful
test of the performances of GeMS on multi-epoch data.
Description:
Magnitude, proper motions and related uncertainties for the stars in
common to the HST sample of Massari et al. (2013ApJ...779...81M) (see
Fig. 3).
Objects:
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RA (ICRS) DE Designation(s)
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18 43 12.76 -32 17 31.6 NGC 6681 = M 70
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