ZTF SN Ia DR2: Exploring SN Ia properties in the vicinity of under-dense environments

TL;DR

This study uses ZTF data to examine how under-dense large-scale environments influence Type Ia supernova properties, finding minimal bias and a correlation between local density and supernova stretch.

Contribution

It is the first to analyze the impact of large-scale under-dense environments on SN Ia light curve properties using Voronoi volumes as local density proxies.

Findings

Moderate dependence of supernova stretch on void proximity

No significant effect of environment on supernova colour

Under-dense environments do not bias supernova analyses

Abstract

The unprecedented statistics of detected Type Ia supernovae (SNe Ia) brought by the Zwicky Transient Facility enables us to probe the impact of the Large-Scale Structure on the properties of these objects. The goal of this paper is to explore the possible impact of the under-dense part of the large-scale structure on the intrinsic SALT2 light curve properties of SNe Ia and uncover possible biases in SN Ia analyses. With a volume-limited selection of ZTF-Cosmo-DR2 Type Ia supernovae overlapping with the SDSS-DR7 survey footprint, we investigate the distribution of their properties with regard to voids detected in the SDSS-DR7 galaxy sample. We further use Voronoi volumes as proxy for local density environments within the large-scale structure. We find a moderate dependency of the stretch toward the localisation around the void centre and none when considering colour. The local Voronoi volumes mostly affect the fraction of low/high stretch supernovae. With the current statistics available, we consider that the impact of high or low local density environment can be considered as a proxy for the colour of the host galaxy. Under-dense environments should not cause any biases in supernova analyses.