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Euclid: Testing the Copernican principle with next-generation surveys

D. Camarena, V. Marra, Z. Sakr, S. Nesseris, A. C. da Silva, J. Garcia-Bellido, P. Fleury, L. Lombriser, M. Martinelli, C. J. A. P. Martins, J. P. Mimoso, D. Sapone, C. Clarkson, S. Camera, C. Carbone, S. Casas, S. Ilić, V. Pettorino, I. Tutusaus, N. Aghanim, B. Altieri, A. Amara, N. Auricchio, M. Baldi, D. Bonino, E. Branchini, M. Brescia, J. Brinchmann, G. P. Candini, V. Capobianco, J. Carretero, M. Castellano, S. Cavuoti, A. Cimatti, R. Cledassou, G. Congedo, L. Conversi, Y. Copin, L. Corcione, F. Courbin, M. Cropper, H. Degaudenzi, F. Dubath, C. A. J. Duncan, X. Dupac, S. Dusini, A. Ealet, S. Farrens, P. Fosalba, M. Frailis, E. Franceschi, M. Fumana, B. Garilli, B. R. Gillis, C. Giocoli, A. Grazian, F. Grupp, S. V. H. Haugan, W. A. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, A. Kiessling, R. Kohley, M. Kunz, H. Kurki-Suonio, P. B. Lilje, I. Lloro, O. Mansutti, O. Marggraf, F. Marulli, R. Massey, M. Meneghetti, E. Merlin, G. Meylan, M. Moresco, L. Moscardini, E. Munari, S. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo López, J. D. Rhodes, G. Riccio, H. -W. Rix, E. Rossetti, R. Saglia, B. Sartoris, A. Secroun, G. Seidel, C. Sirignano, G. Sirri, L. Stanco, C. Surace, P. Tallada-Crespí, A. N. Taylor, I. Tereno, R. Toledo-Moreo, F. Torradeflot, E. A. Valentijn, L. Valenziano, Y. Wang, G. Zamorani, J. Zoubian, S. Andreon, V. Scottez, M. Tenti

Context. The Copernican principle, the notion that we are not at a special location in the Universe, is one of the cornerstones of modern cosmology. Its violation would invalidate the Friedmann-Lemaître-Robertson-Walker metric, causing a major change in our understanding of the Universe. Thus, it is of fundamental importance to perform observational tests of this principle.
Aims. We determine the precision with which future surveys will be able to test the Copernican principle and their ability to detect any possible violations.
Methods. We forecast constraints on the inhomogeneous Lemaître-Tolman-Bondi (LTB) model with a cosmological constant Λ, basically a cosmological constant Λ and cold dark matter (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 ΛCDM and ΛLTB fiducial models. These constraints are compared to the expectations from the Copernican principle.
Results. When considering the ΛCDM 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 ±10% variations depending on the observables and scales considered. On the other hand, when considering a ΛLTB fiducial model, we find that future Euclid data, combined with other current and forthcoming datasets, will be able to detect gigaparsec-scale inhomogeneities of contrast −0.1.
Conclusions. Next-generation surveys, such as Euclid, will thoroughly test homogeneity at large scales, tightening the constraints on possible violations of the Copernican principle.

large-scale structure of Universe / cosmology: observations / cosmological parameters / cosmology: miscellaneous

This paper is published on behalf of the Euclid Consortium.

Astronomy & Astrophysics
Volume 671, Article Number A68, Number of pages 15
2023 March

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia