A closer look at the host-galaxy environment of high-velocity Type Ia supernovae

TL;DR

This study investigates the environments of high-velocity Type Ia supernovae, finding a possible link to older stellar populations, but results are limited by sample bias and dataset constraints.

Contribution

It provides a detailed analysis of the local environments of high-velocity SNe Ia, exploring potential environmental factors influencing their properties.

Findings

HV SNe Ia may be associated with older stellar populations

No definitive correlation due to sample bias and dataset limitations

Results suggest other factors like metallicity could influence supernova characteristics

Abstract

Recent studies suggested that the ejecta velocity of Type Ia supernova (SN Ia) is a promising indicator in distinguishing the progenitor systems and explosion mechanisms. By classifying the SNe Ia based on their ejecta velocities, studies found SNe Ia with high Si II $\lambda$6355 velocities (HV SNe Ia; v>12000 km/s) tend to be physically different from their normal-velocity counterparts (NV SNe Ia). In this work, we revisit the low-$z$ sample studied in previous work and closely look into the spatially resolved environment local to the site of SN explosion. Our results reveal a possible trend (at $2.4\sigma$ significance) that HV SNe Ia are likely associated with older stellar populations than NV SNe Ia. While the trend is inconclusive, the local host-galaxy sample studied in this work is likely skewed toward massive galaxies, limiting the parameter space that we would like to investigate from the original parent sample. Nevertheless, our results do not rule out the possibility that parameters other than the host-galaxy age (such as metallicity) could be the underlying factors driving the differences between HV and NV SNe Ia due to the limitation of our dataset.