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GeMS/GSAOI Photometric and Astrometric Performance in Dense Stellar Fields

Journal
Date Issued
2016
Author(s)
•
Saracino, S.
•
•
Marchetti, E.
•
Ferraro, F. R.
•
Lanzoni, B.
•
Geisler, D.
•
Cohen, R. E.
•
Mauro, F.
•
Villanova, S.
DOI
Abstract
Ground-based imagers at 8 m class telescopes assisted by multi-conjugate adaptive optics are primary facilities with which to obtain accurate photometry and proper motions in dense stellar fields. We observed the central region of the globular clusters Liller 1 and NGC 6624 with the Gemini Multi-conjugate Adaptive Optics System (GeMS) feeding the Gemini South Adaptive Optics Imager (GSAOI) currently available at the Gemini South telescope, under different observing conditions. We characterized the stellar point-spread function (PSF) in terms of FWHM, Strehl ratio (SR), and encircled energy (EE), over the field of view (FOV). We found that, for sub-arcsecond seeing at the observed airmass, we can obtain the diffraction-limited PSF (FWHM ≈ 80 mas), SR ∼ 40%, and EE ≥ 50% with a dispersion around 10% over the FOV of 85″ × 85″, in the K s band. In the J band the best images provide FWHMs between 60 and 80 mas, SR \gt 10 % , and {EE}\gt 40 % . For seeing at the observed airmass exceeding 1″, the performance worsens but it is still possible to perform PSF fitting photometry with 25% EE in J and 40% in K s . We also computed the geometric distortions of GeMS/GSAOI and we obtained corrected images with an astrometric accuracy of ∼1 mas in a stellar field with high crowding.
Volume
833
Issue
1
Start page
111
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...833..111D
Rights
open.access
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