Liger IFS Wavelength Calibration
Presented at Keck Science Meeting 2026
Liger is a next generation imager and integral field spectrograph (IFS) for the Keck All-sky Precision Adaptive-optics (KAPA) system on the Keck I telescope. Liger’s IFS will consist of a slicer assembly and lenslet array with higher spectral resolution capabilities (R=4,000 - 10,000) than other IFS instruments. Enabling Liger’s diverse science cases will require a robust characterization of the IFS wavelength solution, especially across its higher spectral resolution modes. We investigate the calibration of the wavelength solution for the Liger IFS, as well as the current capabilities of the calibration arc lamp sources in Keck I AO. We utilize simulations of Liger’s Lenslet IFS based on optical modeling of the instrument with Zemax, starting with a spectrum of emission lines for each Liger mode from the arc lamps to simulate an arc lamp scan. Our simulations include an end-to-end noise model of the instrument to generate a reduced data cube, which we then analyze to extract the per-lenslet wavelength solution. Initially, we have performed these simulations for a subset of lenslet modes suggesting good wavelength solution characterization in K band, with the future goal of investigating all IFS modes and determining the limiting factors in measuring the wavelength solution. Preliminary analysis of the current arc lamp spectrum at Keck suggests that bands such as Y and H might require additional sources on the Keck I AO calibration bench.
