Expanding covariant cosmography of the local Universe: incorporating the snap and axial symmetry

Abstract

Studies show that the model-independent, fully non-perturbative covariant cosmographic approach is suitable for analyzing the local Universe $(z\lesssim 0.1)$. However, accurately characterizing large and inhomogeneous mass distributions requires the fourth-order term in the redshift expansion of the covariant luminosity distance $d_L(z,\mathbf{n})$. We calculate the covariant snap parameter $\mathbb{S}$ and its spherical harmonic multipole moments using the matter expansion tensor and the evolution equations for lightray bundles. The fourth-order term adds 36 degrees of freedom, since the highest independent multipole of the snap is the 32-pole (dotriacontapole) $(\ell =5)$. Including this term helps to de-bias estimations of the covariant deceleration parameter. Given that observations suggest axially symmetric anisotropies in the Hubble diagram for $z\lesssim 0.1$ and theory shows that only a subset of multipoles contributes to the signal, we demonstrate that only 12 degrees of freedom are needed for a model-independent description of the local universe. We use an analytical axisymmetric model of the local Universe, with data that matches the Zwicky Transient Facility survey, in order to provide a numerical example of the amplitude of the snap multipoles and to forecast precision.

Version accepted by JCAP: additional results and clarifications. (14 + 7 pages)

References in corpus (16)

• The Pantheon+ Analysis: The Full Dataset and Light-Curve Release
• On the Hubble constant tension in the SNe Ia Pantheon sample
• A Test of the Cosmological Principle with Quasars
• Is the Observable Universe Consistent with the Cosmological Principle?
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• Cosmological implications of the anisotropy of ten galaxy cluster scaling relations
• Hints of FLRW Breakdown from Supernovae
• The Cosmic Radio Dipole: Estimators and Frequency Dependence
• On Larger $H_0$ Values in the CMB Dipole Direction
• Anomalies in Physical Cosmology
• Probing the anisotropic expansion from supernovae and GRBs in a model-independent way
• Multipole decomposition of the general luminosity distance 'Hubble law' -- a new framework for observational cosmology
• Dipolar modulation in number counts of WISE-2MASS sources
• The multipole expansion of the local expansion rate
• Covariant cosmography: the observer-dependence of the Hubble parameter
• Cosmography of the Local Universe by Multipole Analysis of the Expansion Rate Fluctuation Field

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• Testing inhomogeneous cosmography in our cosmic neighborhood using CosmicFlows-4
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