ITC Colloquium

Alexandra Amon

Weak lensing with a billion galaxies: New opportunities, challenges and strategies

Weak gravitational lensing provides an immense opportunity to test the standard cosmological model and to probe astrophysics. Over the last decade, it has matured as a high-precision tool with surveys like the Dark Energy Survey, which has imaged 5000 sq degrees and 100M galaxies. Intriguingly, weak lensing surveys have consistently reported a mild cosmological tension:  low values of the clustering amplitude parameter  (S_8) compared to that predicted by Planck primary Cosmic Microwave Background. On the eve of Rubin Observatory’s Legacy Survey of Space and Time (LSST), which will measure weak lensing with billions of galaxies, the challenge is clear: systematics must be controlled to make the most of the next epic decade of data. In this talk, I will present on-going efforts to calibrate observations, in particular, the photometric redshifts of the galaxy sample, and to understand and mitigate astrophysical systematic effects, to maximize weak lensing science. I will demonstrate the pathways to use LSST data to test the cosmological model in the non-linear regime.