文章基本信息

标题：Astrometry with MCAO: HST-GeMS proper motions in the globular cluster NGC 6681
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作者：D. Massari ; D. Massari ; G. Fiorentino 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2016
卷号：595
页码：1-5
DOI：10.1051/0004-6361/201629336
语种：English
出版社：EDP Sciences
摘要：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. 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. Results. We find this to be (μαcosδ,μδ) = (4.09,−3.41)mas yr-1, which matches previous HST/ACS measurements with a very good accuracy of 0.03 mas yr-1 and with a comparable precision (rms of 0.43 mas yr-1). 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.
关键词：astrometry;proper motions;instrumentation: adaptive optics;globular clusters: individual: NGC 6681;galaxies: individual: Sagittarius dSph