The KBC Void: Consistency with Supernovae Type Ia and the Kinematic SZ Effect in a $\Lambda$LTB Model

TL;DR

This paper investigates whether a local under-dense region, modeled as a $ ext{Lambda}$LTB void, aligns with supernovae data and kSZ constraints, potentially easing the Hubble tension.

Contribution

It demonstrates the compatibility of a large local void with supernovae observations and kSZ measurements, and shows this reduces the Hubble constant tension.

Findings

Consistency with supernovae luminosity distances in the local universe.

Reduction of Hubble tension from 3.4σ to 2.75σ when considering the void.

Compatibility of the KBC void with kSZ constraints from SPT and ACT.

Abstract

There is substantial and growing observational evidence from the normalized luminosity density in the near-infrared that the local universe is under-dense on scales of several hundred Megaparsecs. We test whether our parameterization of the observational data of such a "void" is compatible with the latest supernovae type Ia data and with constraints from line-of-sight peculiar velocity motions of galaxy clusters with respect to the cosmic microwave background rest frame, known as the linear kinematic Sunyaev-Zel'dovich (kSZ) effect. Our study is based on the large local void (LLV) radial profile observed by Keenan, Barger, and Cowie (KBC) and a theoretical void description based on the Lema\^itre-Tolman-Bondi model with a nonzero cosmological constant ($\Lambda$LTB). We find consistency with the measured luminosity distance-redshift relation on radial scales relevant to the KBC LLV through a comparison with 217 low-redshift supernovae type Ia over the redshift range $0.0233 < z < 0.15$. We assess the implications of the KBC LLV in light of the tension between "local" and "cosmic" measurements of the Hubble constant, $H_{0}$. We find that when the existence of the KBC LLV is fully accounted for, this tension is reduced from $3.4\sigma$ to $2.75\sigma$. We find that previous linear kSZ constraints, as well as new ones from the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT), are fully compatible with the existence of the KBC LLV.