Metallicity Estimation of Core-Collapse Supernova HII Regions in Galaxies within 30 Mpc

TL;DR

This study measures local metallicities of supernova environments within 30 Mpc, analyzing their distribution across different types and assessing the statistical significance of differences with consideration of measurement uncertainties.

Contribution

It provides a detailed comparison of metallicity distributions for various supernova types using new observations and existing data, highlighting the impact of uncertainties on statistical conclusions.

Findings

Type Ib and Ic supernovae tend to occur in higher metallicity environments.

No statistically significant difference in metallicity distributions among supernova types when considering uncertainties.

Combining data sets reveals a significant difference between Type Ib and Type IIP supernovae metallicities.

Abstract

This work presents measurements of the local HII environment metallicities of core-collapse supernovae (SNe) within a luminosity distance of 30 Mpc. 76 targets were observed at the Isaac Newton Telescope and environment metallicities could be measured for 65 targets using the N2 and O3N2 strong emission line method. The cumulative distribution functions (CDFs) of the environment metallicities of Type Ib and Ic SNe tend to higher metallicity than Type IIP, however Type Ic are also present at lower metallicities whereas Type Ib are not. The Type Ib frequency distribution is narrower (standard deviation $\sim$0.06 dex) than the Ic and IIP distributions ($\sim$0.15 dex) giving some evidence for a significant fraction of single massive progenitor stars; the low metallicity of Type Ic suggests a significant fraction of compact binary progenitors. However, both the Kolmogorov-Smirnov test and the Anderson-Darling test indicate no statistical significance for a difference in the local metallicities of the three SN types. Monte-Carlo simulations reveal a strong sensitivity of these tests to the uncertainties of the derived metallicities. Given the uncertainties of the strong emission methods, the applicability of the tests seems limited. We extended our analysis with the data of the Type Ib/Ic/IIP SN sample from Galbany et al. (2018). The CDFs created with their sample confirm our CDFs very well. The statistical tests, combining our sample and the Galbany et al. (2018) sample, indicate a significant difference between Type Ib and Type IIP with <5% probability that they are drawn from the same parent population.