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

Context. The unprecedented statistics of detected Type Ia supernovae (SNe Ia) brought by the Zwicky Transient Facility (ZTF) enable us to probe the impact of the large-scale structure (LSS) on the properties of these objects. Aims. The goal of this paper is to explore the possible impact of the under-dense part of the LSS on the intrinsic SALT2 light-curve properties of SNe Ia and uncover possible biases in SN Ia analyses. Methods. With a volume-limited selection of ZTF-Cosmo-DR2 SNe Ia overlapping with the SDSS-DR7 survey footprint, we investigated the distribution of their properties with regard to voids detected in the SDSS-DR7 galaxy sample. We further used Voronoi volumes as a proxy for local density environments within the LSS. Results. We find a moderate dependency of the stretch on the localisation around the void centre and none when considering colour. The local Voronoi volumes mostly affect the fraction of low- and high-stretch supernovae. Conclusions. With the presently available statistics, 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 analyses of supernova.