Description
The South Pole Telescope Shirokoff Line Intensity Mapper (SPT-SLIM) experiment is a pathfinder for demonstrating the use of multipixel on-chip spectrometers for millimeter (mm) Line Intensity Mapping (LIM). SPT-SLIM targets the CO rotational transitions from galaxies with redshifts ranging $z\sim0.5$--$3$ to map the large-scale structure of the Universe through hyperspectral imaging. SPT-SLIM achieved first light during the austral summer 2024-2025 observing season, leveraging superconducting filterbanks to provide $R\sim100$ imaging spectroscopy in the 120--180 GHz atmospheric window. Each of the five operational spectrometer devices couples light from an on-sky antenna to a series of 130 spectral filters, each terminated in a lumped-element kinetic inductance detector (KID).
We present early observations demonstrating the instrument and a comprehensive set of spectral calibration measurements of the SLIM submodules. Leveraging laboratory measurements with Fourier transform spectrometers, we have measured the spectral response and mm performance of the spectrometer pixels.
