Combined constraints on deviations of dark energy from an ideal fluid fromEuclidandPlanck

Abstract

Cosmological fluids are commonly assumed to be distributed in a spatially homogeneous way, while their internal properties are described by a perfect fluid. As such, they influence the Hubble-expansion through their respective densities and equation of state parameters. The subject of this paper is an investigation of the fluid-mechanical properties of a dark energy fluid, which is characterised by its sound speed and its viscosity apart from its equation of state. In particular, we compute the predicted spectra for the integrated Sachs-Wolfe effect for our generalised fluid, and compare them with the corresponding predictions for weak gravitational lensing and galaxy clustering, which had been computed in previous work. We perform statistical forecasts and show that the integrated Sachs-Wolfe signal obtained by cross correlating Euclid galaxies with Planck temperatures, when joined to galaxy clustering and weak lensing observations, yields a percent sensitivity on the dark energy sound speed and viscosity. We prove that the iSW effect provides strong degeneracy breaking for low sound speeds and large differences between the sound speed and viscosity parameters.

H i and cosmological constraints from intensity mapping, optical and CMB surveys

“…We summarise the (marginalised) forecasted constraints in Table 5. We note that we have checked our Fisher matrix code results are in agreement with the ones presented in Majerotto et al (2016) when we consider a Stage IV galaxy survey only and constrain {lnf σ8, lnbgσ8, lnDA, lnH} using the P gg (k, µ, z) power spectrum. We see that we get very good constraints on the growth of structure, the Hubble parameter and the angular diameter distance across a wide range of redshifts corresponding to the era where dark energy is starting to become important (0.7 < z < 1.4).…”

“…In our forecasts for such a survey we will use the number density of galaxiesn given in Majerotto et al (2016), where the predicted redshift distribution has been split into 14 bins with ∆z = 0.1.…”

Testing extended Jordan-Brans-Dicke theories with future cosmological observations

“…where the subscript ij refers to the redshift bins around z i and z j , with W i (z) is the window function (see [69] for more details). The tomographic overall radial distribution function of galaxies for a Euclid-like photometric survey is [30]:…”

The cross-correlation between 3D cosmic shear and the integrated Sachs–Wolfe effect

“…The effect vanishes in the linear regime of structure growth during matter domination, so that observations probe the relatively late times at which the dark energy contribution to the density becomes appreciable. This cosmological sensitivity was demonstrated by Vielva et al (2006); Pietrobon et al (2006);McEwen et al (2007); Giannantonio et al (2008); Ho et al (2008); Giannantonio et al (2014); Planck Collaboration (2015); Majerotto et al (2016).…”