2015/03/29 by Mattia Libralato, M. Libralato, Andrea Bellini +9 · 1 citation
Engineering · Physics and Astronomy · #Astrometry #Astronomical Observations and Instrumentation #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Bulge #Calibration #Distortion (music) #Galactic Center #Globular cluster #Horizontal branch #Physics #Proper motion #Stars #Stellar, planetary, and galactic studies #astro-ph.IM #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stv674
11 pages, 10 figures (some in low res), 1 table. Accepted for publication in MNRAS on March 25, 2015. The FORTRAN routine will be soon made available at http://groups.dfa.unipd.it/ESPG/ , and via email request to the first author
arxiv created 2015/03/29 · openalex publication_date 2015/04/28 · arxiv updated 2015/06/24 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present a new reduction pipeline for the VIRCAM@VISTA detector and describe the method developed to obtain high-precision astrometry with the VISTA Variables in the Vía Láctea (VVV) data set. We derive an accurate geometric-distortion correction using as calibration field the globular cluster NGC 5139, and showed that we are able to reach a relative astrometric precision of about 8 mas per coordinate per exposure for well-measured stars over a field of view of more than 1 deg2. This geometric-distortion correction is made available to the community. As a test bed, we chose a field centred around the globular cluster NGC 6656 from the VVV archive and computed proper motions for the stars within. With 45 epochs spread over four years, we show that we are able to achieve a precision of 1.4 mas yr−1 and to isolate each population observed in the field (cluster, Bulge and Disc) using proper motions. We used proper-motion-selected field stars to measure the motion difference between Galactic disc and bulge stars. Our proper-motion measurements are consistent with UCAC4 and PPMXL, though our errors are much smaller. Models have still difficulties in reproducing the observations in this highly reddened Galactic regions.