High-precision astrometry with VVV - I. An independent reduction pipeline for VIRCAM@VISTA

M. Libralato, A. Bellini, L. R. Bedin, J. Anderson, G. Piotto, V. Nascimbeni, I. Platais, D. Minniti, M. Zoccali

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)1664-1673
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 10 Apr 2015


  • Astrometry
  • Galaxy: general
  • Globular clusters: individual: NGC 5139
  • Globular clusters: individual: NGC 6656
  • Proper motions
  • Techniques: image processing

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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