A local infall from a cosmographic analysis of Pantheon+

TL;DR

This paper performs a model-independent analysis of Pantheon+ supernova data, revealing a significant local infall likely caused by an overdensity within approximately 120 Mpc, affecting key cosmological parameters.

Contribution

It introduces a model-independent method to analyze supernova data and identifies a local infall related to an overdensity, impacting measurements of H_0, q_0, and j_0.

Findings

Detection of a significant local infall due to an overdensity

Dependence of cosmological parameters on redshift cut and peculiar velocity modeling

Implication of local structure on cosmological measurements

Abstract

We present a model independent analysis of the Pantheon+ supernova sample and study the dependence of the recovered values of $H_0$, $q_0$ and $j_0$ on the redshift cut and on the modeling of peculiar velocities. In addition to the bulk velocity discussed previously, we also find a significant infall that we attribute to the presence of an overdensity out to a radius of $R\simeq 120h^{-1}$Mpc.