SPT-SLIM: A Line Intensity Mapping Pathfinder for the SPT

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Modern cosmology has revealed a wealth of information about nature of the Universe. Two mysteries endure. Inflation, which caused the rapid expansion of the very early Universe, and Dark Energy, which is important in the way the Universe expands today. These phenomena are studied by measuring the distance between galaxies over time. Line intensity mapping is a new technique that will allow for even more sensitive such measurements, but to make such measurement requires a new kind of instrument. This instrument consists of a camera in which every individual pixel is a spectrometer. The South Pole Telescope Line Intensity Line Mapper will demonstrate a novel technology that uses superconducting circuits built on a silicon wafer and cooled to 0.1 degrees above absolute zero. The South Pole is one of only a few places on Earth where such observations are possible. This program will provide U. Chicago students with hands-on training in cutting-edge instrumentation and thin film fabrication, which have applications in a wide variety of fields. Through Design Apprenticeship Program connecting the Chicago South Side artistic community with University of Chicago research laboratories, local teenagers will learn and apply design and construction skills. Measuring the large-scale structure of the early Universe is key to understanding the nature of dark energy and inflation. Performing these measurements by targeting atomic and molecular emission lines also probes the astrophysics of the first stars and galaxies. This project will demonstrate a new technique that will deploy a millimeter-wavelength integral field unit (IFU) to the 10-meter South Pole Telescope (SPT). The SPT Summertime Line Intensity Mapper (SPT-SLIM) will include 18 dual-polarization pixels, each coupled to a spectrometer with resolving power of R ~ 300, covering the 150 GHz atmospheric window and will observe during the Austral summer season. SPT-SLIM is sensitive to carbon monoxide (CO) line emission from high-redshift galaxies (0.4 z 2.8). This instrument will provide unique capability in the new field of line intensity mapping (LIM). SPT-SLIM will demonstrate that multi-pixel on-chip spectrometers meet this need and develop the necessary observational strategies and data analysis techniques using actual on-sky data. In one month of observation at SPT this pathfinder instrument will detect the CO power spectrum at 10-sigma and constrain the molecular gas fraction in the full population of z ~ 2 galaxies. SPT-SLIM will also be a powerful tool for future pointed observations of individual galaxies, efficiently identifying redshifts of sources identified in continuum surveys over a wide range of cosmic history. This award addresses and advances the science objectives and goals of the NSF's "Windows on the Universe: The Era of Multi-Messenger Astrophysics" Big Idea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.