Euclid: Testing the Copernican principle with next-generation surveys

Abstract

The Copernican principle, the notion that we are not at a special location in the Universe, is one of the cornerstones of modern cosmology and its violation would invalidate the Friedmann-Lema\^ıtre-Robertson-Walker (FLRW) metric, causing a major change in our understanding of the Universe. Thus, it is of fundamental importance to perform observational tests of this principle. We determine the precision with which future surveys will be able to test the Copernican principle and their ability to detect any possible violations. We forecast constraints on the inhomogeneous Lema\^ıtre-Tolman-Bondi model with a cosmological constant $\Lambda$ ($\Lambda$LTB), basically a cosmological constant $\Lambda$ and cold dark matter ($\Lambda$CDM) model, but endowed with a spherical inhomogeneity. We consider combinations of currently available data and simulated Euclid data, together with external data products, based on both $\Lambda$CDM and $\Lambda$LTB fiducial models. These constraints are compared to the expectations from the Copernican principle. When considering the $\Lambda$CDM fiducial model, we find that Euclid data, in combination with other current and forthcoming surveys, will improve the constraints on the Copernican principle by about $30\%$, with $\pm 10\%$ variations depending on the observables and scales considered. On the other hand, when considering a $\Lambda$LTB fiducial model, we find that future Euclid data, combined with other current and forthcoming data sets, will be able to detect Gpc-scale inhomogeneities of contrast $-0.1$. Next-generation surveys, such as Euclid, will thoroughly test homogeneity at large scales, tightening the constraints on possible violations of the Copernican principle.

15 pages, 5 figures, 3 tables, v2 reflects version accepted for publication in A&A

References in corpus (17)

• The Clustering of the SDSS DR7 Main Galaxy Sample I: A 4 per cent Distance Measure at z=0.15
• The DESI Experiment Part I: Science,Targeting, and Survey Design
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Baryon acoustic oscillations with Lyman-$\alpha$ forests
• Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field
• Confronting Lemaitre-Tolman-Bondi models with Observational Cosmology
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Large-scale Structure Catalogs for Cosmological Analysis
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• Looking the void in the eyes - the kSZ effect in LTB models
• Scalar Perturbations on Lemaitre-Tolman-Bondi Spacetimes
• Precision cosmology defeats void models for acceleration
• Extending the supernova Hubble diagram to z~1.5 with the Euclid space mission
• Probing spatial homogeneity with LTB models: a detailed discussion
• Do supernovae indicate an accelerating universe?
• A void in the Hubble tension? The end of the line for the Hubble bubble
• Euclid: constraining dark energy coupled to electromagnetism using astrophysical and laboratory data
• CMASS galaxy sample and the ontological status of the cosmological principle

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