KiDS + GAMA: constraints on horndeski gravity from combined large-scale structure probes

Abstract

We present constraints on Horndeski gravity from a combined analysis of cosmic shear, galaxy-galaxy lensing and galaxy clustering from 450 deg 2 of the Kilo-Degree Survey (KiDS) and the Galaxy And Mass Assembly (GAMA) survey. The Horndeski class of dark energy/modified gravity models includes the majority of universally coupled extensions to ΛCDM with one scalar field in addition to the metric. We study the functions of time that fully describe the evolution of linear perturbations in Horndeski gravity. Our results are compatible throughout with a ΛCDM model. By imposing gravitational wave constraints, we fix the tensor speed excess to zero and consider a subset of models including e.g. quintessence and f (R) theories. Assuming proportionality of the Horndeski functions α B and α M (kinetic braiding and the Planck mass run rate, respectively) to the dark energy density fraction Ω DE (a) = 1 − Ω m (a), we find for the proportionality coefficientsα B = 0.20 +0.20 −0.33 andα M = 0.25 +0.19 −0.29 . Our value of S 8 ≡ σ 8√ Ω m /0.3 is in better agreement with the Planck estimate when measured in the enlarged Horndeski parameter space than in a pure ΛCDM scenario. In our joint three-probe analysis we report a downward shift of the S 8 best fit value from the Planck measurement of ∆S 8 = 0.016 +0.048 −0.046 in Horndeski gravity, compared to ∆S 8 = 0.059 +0.040 −0.039 in ΛCDM. Our constraints are robust to the modelling uncertainty of the non-linear matter power spectrum in Horndeski gravity. Our likelihood code for multi-probe analysis in both ΛCDM and Horndeski gravity is publicly available at https://github.com/alessiospuriomancini/KiDSHorndeski.

Effective field theory of dark energy: A review

“…On top of this, asking for sub-luminal propagation of scalar and tensor perturbations reduces drastically the marginalized contours of the parameters (see Figure 17 top panels). Despite the different parameterization with respect to the model previously discussed [199,208], the tendency of the data to favor a lower effective Planck mass and a lower propagation speed for tensor modes is recovered. Furthermore, with the aim to be more general, one can be led to increase by one the number of free parameters characterizing each EFT function.…”

“…These are instead very important in the interpretation of data since substantial part of GC, CMB lensing and WL data originates from non-linear scales. A phenomenological way to mimic screening mechanisms has been recently introduced [141,208] which highlighted the urgency of the inclusion for nonlinearities in the data analysis as these have been proven to increase the constraints on the EFT functions [219]. In this regard, a number of pioneer work contributed to incorporate non-linear effects to the EFT framework [57,59,60].…”

“…The constraints display a neat preference for a positive value for the braiding, negative for the running Planck mass and a sub-luminal propagation of tensor modes. This parameterization was further investigated in light of KiDS+GAMA data considering luminal propagation of tensor modes [208]. While the constraints on cosmological parameters are compatible with ΛCDM, a preference for positive values of α M and α B is found.…”

Calibration of systematics in constraining modified gravity models with galaxy cluster mass profiles

“…refs. [8][9][10][11]). Among the broad range of gravity tests at cosmological scales, galaxy clusters offer an interesting field of investigation (e.g.…”

hi_class background evolution, initial conditions and approximation schemes

“…2 The structure of the code and the modifications with respect to the CLASS code are described in detail in the first hi_class paper [55]. hi_class can be used to explore different aspects of gravitational theories and their cosmological implications [66][67][68][69][70], test models against current data [19,[71][72][73] or in preparation for future experiments [36,74,75]. 3 hi_class has been cross-validated against other codes both implementing a general EFTDE framework (e.g.…”