An effective $\boldsymbolΛ$-Szekeres modelling of the local Universe with Cosmicflows-4
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| Main Authors: | , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866914522657193984 |
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| author | Galoppo, Marco Giani, Leonardo Hills, Morag Valade, Aurélien |
| author_facet | Galoppo, Marco Giani, Leonardo Hills, Morag Valade, Aurélien |
| contents | We develop an effective description of the local cosmic environment, namely, for redshift $z \lesssim 0.1$, to quantify the bias induced by local structure on cosmological observables. Our approach models the metric of the nearby Universe as a superposition of multi-structured $Λ$-Szekeres patches, calibrated against the HAMLET peculiar velocity and density field reconstructions of Cosmicflows-4. From this framework we compute the fully inhomogeneous and anisotropic quasilocal expansion field predicted by our model, and use it to assess the impact of local structure on estimates of $H_0$. For this purpose we analyse low-redshift Type Ia supernovae from the Pantheon+ catalogue. We find that accounting for the local structure increases the Hubble tension, yielding a shift in the best-fit value of the Hubble constant of order $ΔH_0 \approx 0.5\ \mathrm{km\,s^{-1}Mpc^{-1}}$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_16591 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | An effective $\boldsymbolΛ$-Szekeres modelling of the local Universe with Cosmicflows-4 Galoppo, Marco Giani, Leonardo Hills, Morag Valade, Aurélien Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We develop an effective description of the local cosmic environment, namely, for redshift $z \lesssim 0.1$, to quantify the bias induced by local structure on cosmological observables. Our approach models the metric of the nearby Universe as a superposition of multi-structured $Λ$-Szekeres patches, calibrated against the HAMLET peculiar velocity and density field reconstructions of Cosmicflows-4. From this framework we compute the fully inhomogeneous and anisotropic quasilocal expansion field predicted by our model, and use it to assess the impact of local structure on estimates of $H_0$. For this purpose we analyse low-redshift Type Ia supernovae from the Pantheon+ catalogue. We find that accounting for the local structure increases the Hubble tension, yielding a shift in the best-fit value of the Hubble constant of order $ΔH_0 \approx 0.5\ \mathrm{km\,s^{-1}Mpc^{-1}}$. |
| title | An effective $\boldsymbolΛ$-Szekeres modelling of the local Universe with Cosmicflows-4 |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2512.16591 |