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|Title:||Astrometry with MCAO: HST-GeMS proper motions in the globular cluster NGC 6681||Authors:||Massari, D.
Stetson, P. B.
Veran, J. -P.
|Issue Date:||2016||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||595||First Page:||L2||Abstract:||<BR /> Aims: For the first time the astrometric capabilities of the Gemini Multi-Conjugate Adaptive Optics System (GeMS) facility at the Gemini South Adaptive Optics Imager (GSAOI) camera on Gemini-South are tested to quantify the accuracy in determining stellar proper motions in the Galactic globular cluster NGC 6681. <BR /> Methods: Proper motions from the Hubble Space Telescope (HST) for a sample of its stars are already available, allowing 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-Advanced Camera for Survey (ACS) images to recover the relative proper motion of the Sagittarius dwarf spheroidal galaxy with respect to NGC 6681. <BR /> Results: We find this to be (μ<SUB>α</SUB>cosδ,μ<SUB>δ</SUB>) = (4.09,-3.41)mas yr<SUP>-1</SUP>, which matches previous HST/ACS measurements with a very good accuracy of 0.03 mas yr<SUP>-1</SUP> and with a comparable precision (rms of 0.43 mas yr<SUP>-1</SUP>). <BR /> Conclusions: This study successfully demonstrates that high-quality proper motions can be measured for relatively large fields of view (85''× 85'') with MCAO-assisted, ground-based cameras and provides a first, successful test of the performances of GeMS on multi-epoch data. <P />The final reduced data (FITS files) are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://220.127.116.11">http://18.104.22.168</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/595/L2">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/595/L2</A>||Acknowledgments:||Based onobservations obtained at the Gemini Observatory, acquired through the GeminiScience Archive and processed using the Gemini IRAF package. D.M. and G.F.have been supported by the FIRB 2013 (MIUR grant RBFR13J716)||URI:||http://hdl.handle.net/20.500.12386/26699||URL:||https://www.aanda.org/articles/aa/abs/2016/11/aa29336-16/aa29336-16.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201629336||Bibcode ADS:||2016A&A...595L...2M||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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