Constraining a constant and tomographic Coupled Dark Energy model with low and high redshift probes

The current ΛCDM concordance model has been widely successful in describing our Universe. However, crucial questions, such as the H0 tension, remain unanswered and are becoming increasingly critical with the continuous release of high-precision cosmological data. This has led to the exploration of modified ΛCDM models, one of them being the coupled quintessence, or Coupled Dark Energy (CDE) model. Here, we perform for the first time a tomographic analysis of coupled dark energy, where the coupling strength is parametrised and constrained in different redshift bins. We employ cosmic microwave background data from Planck, ACT and SPT, showing the impact of different choices that can be made in combining these datasets. Then, we use a range of low redshift probes to test CDE cosmologies, both for a constant and a tomographic coupling. In particular, we use for the first time data from weak lensing, galaxy clustering, and 3x2pt galaxy-galaxy lensing cross-correlation data. For CMB and background datasets, a tomographic coupling allows for β values up to one order of magnitude larger than in previous works, in particular at z smaller than 1. The use of 3x2pt analysis then becomes important to constrain β at low redshifts, even when coupling is allowed to vary: for 3x2pt we find, at z between 0.5 and 1, β = 0.018+0.007 −0.011, comparable to what CMB and background datasets would give for a constant coupling. This makes upcoming galaxy surveys potentially powerful probes to test CDE models at low redshifts.