Swimming with ShARCS: Comparison of On-sky Sensitivity With Model Predictions for ShaneAO on the Lick Observatory 3-meter Telescope

TL;DR

This paper evaluates the on-sky sensitivity of the ShaneAO system at Lick Observatory, comparing actual measurements with model predictions, and demonstrates significant improvements over the previous system in sensitivity and efficiency.

Contribution

The study presents the first-light sensitivity measurements of ShaneAO and validates a model predicting its enhanced performance compared to the previous system, IRCAL.

Findings

ShaneAO achieves 20% higher throughput in JHK bands.

ShaneAO enables imaging of objects 1-2 magnitudes fainter.

Faster signal-to-noise ratio attainment by a factor of 10-13.

Abstract

The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS - Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the previous infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20\% higher throughput across the $JHK$ bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We highlight the improvements in performance over the previous AO system and its camera, IRCAL.