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

Abstract

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 that SNe Ia with high $\mathrm{Si}\, {\rm{\small II}}\, \lambda 6355$ velocities (HV SNe Ia; $v \gtrsim 12\,000$ km s−1) 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 2.4σ 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 towards 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 data set.