Designing the SPT-3G+ cryostat to support galaxy cluster detection at millimeter wavelengths
Measuring the evolution of the large-scale structure of the universe can probe fundamental physics like the nature of cosmic inflation, the evolution of dark energy, and the mass of the neutrino. Galaxy clusters are the largest gravitationally bound objects in the universe and are useful probes of structure, in particular sensitive to the amplitude of matter fluctuations and matter density. Galaxy clusters are observable at millimeter wavelengths by cryogenic cameras using the thermal Sunyaev-Zel’dovich (tSZ) effect due to cosmic microwave background (CMB) photons scattering off hot electrons in the intra-cluster medium. The surface brightness of the tSZ effect is redshift independent, making it a useful probe of the evolution of structure formation out to high redshift. These high-redshift candidates (z > 2) remain difficult to detect due to correlated dust emission, which necessitates multi-frequency coverage. To enable improved measurements of the tSZ effect, the SPT-3G+ cryostat was designed to support the next-generation 100 mK camera for the South Pole Telescope (SPT), scheduled for deployment in 2028-2029. This cryostat leverages advancements in metamaterial optics and prioritizes modularity with seven individual optics tubes comprising the focal plane to pave the way for testing new detector technologies. In this talk, I describe the design metrics and the analytics that were used in the design of this instrument. I also present a catalog of 217 galaxy clusters over 57 square degrees of sky centered around the Euclid Deep Field-South using data from the SPT-3G camera. Finally, I will show preliminary results of a new SPT-3G cluster catalog, which aims to extend sky coverage by 5,000 square degrees, detecting over 6,800 galaxy clusters in the SPT-3G Wide survey.
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