Bounds from ISW-galaxy cross-correlations on generalized covariant Galileon models

Abstract

Several modified cosmological models exist, which also try to address the tensions between data and predictions of the Λ-CDM model. Galileon models are particular scalar tensor theories that represent one such possibility. While it is commonly understood that there may be inconsistencies between predictions of some Galileon models and observations, in particular concerning ISW-galaxy cross-correlations, there is no proof yet that these models are completely ruled out. Indeed, by using a specific background in the generalized covariant Galileon theory known as the the tracker solution, here we show that, after imposing all standard theoretical stability constraints, it is still possible to identify a region in the parameter space of the model that allows for positive ISW-galaxy cross-correlations. By a physical interpretation in terms of a chi-square analysis, we confirm the expectation that in this viable region the predictions of generalized covariant Galileon theory on the tracker solution background have higher likelihood when they approach the physics of the Λ-CDM model.