Abstract
The combination and cross-correlation of the upcoming Euclid data with cosmic microwave background (CMB) measurements is a source of great expectation since it will provide the largest lever arm of epochs, ranging from recombination to structure formation across the entire past light cone. In this work, we present forecasts for the joint analysis of Euclid and CMB data on the cosmological parameters of the standard cosmological model and some of its extensions. This work expands and complements the recently published forecasts based on Euclid-specific probes, namely galaxy clustering, weak lensing, and their cross-correlation. With some assumptions on the specifications of current and future CMB experiments, the predicted constraints are obtained from both a standard Fisher formalism and a posterior-fitting approach based on actual CMB data. Compared to a Euclid-only analysis, the addition of CMB data leads to a substantial impact on constraints for all cosmological parameters of the standard Λ-cold-dark-matter model, with improvements reaching up to a factor of ten. For the parameters of extended models, which include a redshift-dependent dark energy equation of state, non-zero curvature, and a phenomenological modification of gravity, improvements can be of the order of two to three, reaching higher than ten in some cases. The results highlight the crucial importance for cosmological constraints of the combination and cross-correlation of Euclid probes with CMB data.
Highlights
IntroductionThe apparent accelerated expansion of the Universe at recent cosmological epochs, revealed through the luminosity-distance relation of type Ia supernovae (SN, see Abbott et al 2019 and references therein), and confirmed independently by the other main cosmological probes (see Planck Collaboration 2020; eBOSS Collaboration 2020, and references therein) is one of the greatest puzzles of modern cosmology
The apparent accelerated expansion of the Universe at recent cosmological epochs, revealed through the luminosity-distance relation of type Ia supernovae (SN, see Abbott et al 2019 and references therein), and confirmed independently by the other main cosmological probes is one of the greatest puzzles of modern cosmology
We present the detailed recipes we adopted during our implementation of the Fisher matrix formalism, and for the computation of forecasts of the different cosmological probes considered in the joint Euclid×cosmic microwave background (CMB) analysis
Summary
The apparent accelerated expansion of the Universe at recent cosmological epochs, revealed through the luminosity-distance relation of type Ia supernovae (SN, see Abbott et al 2019 and references therein), and confirmed independently by the other main cosmological probes (see Planck Collaboration 2020; eBOSS Collaboration 2020, and references therein) is one of the greatest puzzles of modern cosmology. Probing and unveiling the physical nature of the DE requires us to measure its effects on both the cosmological geometry/expansion, and its dynamics. Both effects leave imprints at low redshift and can be observed through several probes, including SN, baryon acoustic oscillations (Percival 2017), the full power spectrum of galaxy clustering (GC, Wang et al 2019) and weak lensing (WL, Munshi et al 2020), galaxy cluster number counts (Lacasa & Rosenfeld 2016) and their cross-correlations with the CMB (Ballardini et al 2019). Rubin Observatory (VRO, formerly the Large Synoptic Survey Telescope, Kahn 2018), and the Roman Space Telescope (formerly the Wide Field InfraRed Survey Telescope, Akeson et al 2019)
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