The Large-Scale Environments of Type Ia Supernovae: Evidence for a Metallicity Bias in the Rate or Luminosity of Prompt Ia Events

TL;DR

This study investigates the environments of Type Ia supernovae using SDSS data, revealing a metallicity bias that influences the rate or luminosity of prompt SNe Ia, especially in star-forming galaxies.

Contribution

It provides evidence that the environment and metallicity of host galaxies affect the occurrence and brightness of prompt Type Ia supernovae, highlighting a metallicity bias.

Findings

SN Ia in blue, star-forming galaxies prefer low-density regions.

No significant environment dependence for SNe Ia in red galaxies.

Prompt SNe Ia are more common or luminous in metal-poor systems.

Abstract

Using data drawn from the Sloan Digital Sky Survey (SDSS) and the SDSS-II Supernova Survey, we study the local environments of confirmed type Ia supernovae (SNe Ia) in the nearby Universe. At 0.05 < z < 0.15, we find that SN Ia events in blue, star-forming galaxies occur preferentially in regions of lower galaxy density relative to galaxies of like stellar mass and star-formation rate, while SNe Ia in nearby red galaxies show no significant environment dependence within the measurement uncertainties. Even though our samples of SNe in red hosts are relatively small in number, tests on simulated galaxy samples suggest that the observed distribution of environments for red SN Ia hosts is in poor agreement with a cluster type Ia rate strongly elevated relative to the field rate. Finally, after considering the impact of galaxy morphology, stellar age, stellar metallicity, and other relevant galaxy properties, we conclude that the observed correlation between the SN Ia rate and environment in the star-forming galaxy population is likely driven by a gas-phase metallicity effect, such that prompt type Ia supernovae occur more often or are more luminous in metal-poor systems.