Swimming with ShARCS: comparison of on-sky sensitivity with model predictions for ShaneAO on the Lick Observatory 3-meter telescope

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.

A Sub-Neptune-sized Planet Transiting the M2.5 Dwarf G 9-40: Validation with the Habitable-zone Planet Finder

“…To constrain contamination from background sources and study the possibility that astrophysical false positives could be the source of the transits (e.g., eclipsing binaries or background eclipsing binaries), we performed high-contrast adaptive optics (AO) imaging of G 9-40 using the 3 m Shane Telescope at Lick Observatory on November 25, 2018. We performed the AO imaging using the upgraded ShARCS camera (Srinath et al 2014) in the K s bandpass. We observed the star using a 5-point dither pattern (see e.g., Furlan et al 2017), imaging the star at the center of the detector and in each quadrant.…”

“…At a distance of d = 27.9 pc, G 9-40b is currently the second closest plan-gstefansson@astro.princeton.edu etary system discovered by the K2 mission. G 9-40b was originally identified as a planet candidate in K2 Campaign 16 by Yu et al (2018), and here we perform the necessary observations to validate the planet candidate as a bona-fide planet through precision ground-based diffuser-assisted transit photometry using the Astrophysical Research Consortium Telescope Imaging Camera (ARCTIC) (Huehnerhoff et al 2016) on the Astrophysical Research Consortium (ARC) 3.5m Telescope at Apache Point Observatory, adaptive optics imaging using the ShaneAO instrument (Srinath et al 2014) on the 3m Shane Telescope at Lick Observatory, and precision near-infrared (NIR) radial velocities obtained with the Habitable-zone Planet Finder (HPF) Spectrograph (Mahadevan et al 2012(Mahadevan et al , 2014. Using the HPF NIR spectra, we provide precise spectroscopic parameters using an empirical spectral-matching technique and use the spectra for precision velocimetry to provide an upper bound on the mass of G 9-40b.…”

ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

“…With the laser guidestar, the system has full sky coverage with performance dependent on proximity of a natural tip/tilt star, airmass, and seeing conditions. Unique aspects of the new system from a science prospective include: 5,6 • Detector sampling: 0.035 arcseconds per pixel • Science detector: Hawaii2RG, 80% QE in the near IR, 70% 0.7 to 1.0 µm • On-axis imaging Strehl: see Figure 1 • Long-exposure imaging stability: hold to diffraction-limit for one hour (goal after flexure model) • Spectral resolution: R=500 grism (may be upgraded in the near future to R=2000) • Slit width: 0.1 arcseconds • Slit angle on sky: adjustable using Cassegrain rotator • Long-exposure spectroscopic stability: hold to 1/2 slit width for 4 hours (goal after flexure model) • Minimum brightness natural guide star: m v =13 • Minimum brightness tip/tilt guide star: m v =18 • Infrared sensitivity: m K = 20 to m J = 23 • Camera readout modes: Correlated double-sampling (CDS), up the ramp (UTR), sub-frame region of interest (ROI), quick take • Exposure support: Multiple frame co-added, automated nod and expose coordinated with telescope (snapi-diff, box-4, box-5), automated darks sequence based of history of science exposures • Observations support: automatic data logging, automatic data archiving Unique aspects from an engineering prospective include:…”

Commissioning ShARCS: the Shane adaptive optics infrared camera-spectrograph for the Lick Observatory Shane 3-m telescope

“…We measure a FWHM of 0.188 , while the diffraction limit in Brγ is 0.149 . Srinath et al 2014 compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. 10 Figure 6 shows a 20 ×20 portion of the globular cluster M92.…”