First performance of the gems + gmos system. Part1. Imaging

TL;DR

This paper reports on the initial performance assessment of the GeMS+GMOS system during commissioning, demonstrating significant improvements in image quality and astrometric precision in visible imaging of globular clusters.

Contribution

First evaluation of GeMS+GMOS system performance in visible imaging, including photometric, astrometric, and guide star impact analysis during commissioning.

Findings

Achieved at least 2x improvement over natural seeing in FWHM.

Astrometric precision better than 8 mas absolute, 50 mas relative.

Guide star selection influences image quality performance.

Abstract

During the commissioning of the Gemini MCAO System (GeMS), we had the opportunity to obtain data with the Gemini Multi-Object Spectrograph (GMOS), the most utilised instrument at Gemini South Observatory, in March and May 2012. Several globular clusters were observed in imaging mode that allowed us to study the performance of this new and untested combination. GMOS is a visible instrument, hence pushing MCAO toward the visible.We report here on the results with the GMOS instruments, derive photometric performance in term of Full Width Half Maximum (FWHM) and throughput. In most of the cases, we obtained an improvement factor of at least 2 against the natural seeing. This result also depends on the Natural Guide Star constellation selected for the observations and we then study the impact of the guide star selection on the FWHM performance.We also derive a first astrometric analysis showing that the GeMS+GMOS system provide an absolute astrometric precision better than 8mas and a relative astrometric precision lower than 50 mas.