How to see the invisible: Using the dark matter distribution to test our cosmological model

April 3, 2023

Princeton researchers led by graduate student Roohi Dalal, in collaboration with astronomers at Carnegie Mellon University and various institutions in Japan, announced today new cosmological results from an analysis of deep imaging data from the Subaru Hyper Suprime-Cam (HSC) survey.  Measuring the weak gravitational lensing signal from 25 million galaxies with redshifts between 0.3 and 1.5, they constrained a quantity termed S_8, which determines how strongly dark matter is clustered in the universe. In three different statistical approaches to the S_8 determination, the HSC team found S_8=0.776 +/- 0.032.  The clustering of dark matter can also be measured from fluctuations in the Cosmic Microwave Background (CMB) in the early universe, and they find a significantly larger value, S_8 = 0.83.  This result adds to a number of recent analyses of gravitational lenses, showing a tension with the CMB, hinting at the possibility that our standard cosmological model in which these results are interpreted may need modification. 

More details may be found in the Princeton University news story and website listing a series of papers to be submitted to Physical Review D 

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