Johannes Lange tells us about his recent work with collaborators constraining cosmological parameters, in particular S8, using the non-linear scales in the Dark Energy Survey (DES), the Kilo Degree Survey (KiDS) and the Baryon Oscillation Spectroscopic Survey (BOSS).

They generate predictions for the non-linear scales via the Aemulus suite of simulations, which ran with a variety of cosmological parameters. To connect the simulations’ halos with galaxy observations they use a halo occupation distribution (HOD) model to generate a large number of sets of mock galaxies. The halo model parameters are then marginalised over when comparing the mocks to observations, ultimately giving the final cosmology constraints.

As with more or less all other large scale structure probes nowadays they find a mild tension between their constraints and predictions for S8 coming from CMB observations and the LCDM model.

Johannes: https://johannesulf.github.io/
Paper: https://arxiv.org/abs/2301.08692

halotools code: https://github.com/astropy/halotools
dsigma code: https://github.com/johannesulf/dsigma