Evidence for Two Distinct Populations of Type Ia Supernovae

TL;DR

This study reveals two distinct populations of Type Ia supernovae based on spectral diversity and their host galaxy environments, indicating different progenitor origins related to galaxy evolution.

Contribution

It provides evidence linking spectral diversity of SNe Ia to their environments, suggesting different progenitor populations based on velocity and host galaxy properties.

Findings

High-velocity SNe Ia are concentrated in brighter, inner galaxy regions.

High-velocity SNe Ia tend to occur in larger, more luminous hosts.

Spectral diversity correlates with progenitor age and metallicity.

Abstract

Type Ia supernovae (SNe Ia) have been used as excellent standardizable candles for measuring cosmic expansion, but their progenitors are still elusive. Here we report that the spectral diversity of SNe Ia is tied to their birthplace environments. We find that those with high-velocity ejecta are substantially more concentrated in the inner and brighter regions of their host galaxies than are normal-velocity SNe Ia. Furthermore, the former tend to inhabit larger and more-luminous hosts. These results suggest that high-velocity SNe Ia likely originate from relatively younger and more metal-rich progenitors than normal-velocity SNe Ia, and are restricted to galaxies with substantial chemical evolution.