An H-alpha survey of the host environments of 77 type IIn supernovae within z<0.02

TL;DR

This study analyzes the environments of 77 type IIn supernovae using H-alpha imaging, revealing diverse progenitor paths and challenging the assumption that all originate from luminous blue variables.

Contribution

It provides the largest environmental analysis of SNe IIn, showing that most do not follow H-alpha emission, indicating multiple progenitor scenarios.

Findings

Approximately 60% of SNe IIn have high-mass progenitors like LBVs.

About 40% of SNe IIn are not associated with H-alpha emission.

Some SNe IIn show H-alpha association, suggesting diverse progenitor origins.

Abstract

Type IIn supernovae (SNe\,IIn) are an uncommon and highly heterogeneous class of SN where the SN ejecta interact with pre-existing circumstellar media (CSM). Previous studies have found a mass ladder in terms of the association of the SN location with H$\alpha$ emission and the progenitor masses of SN classes. In this paper, we present the largest environmental study of SNe\,IIn. We analyse the H$\alpha$ environments of 77 type IIn supernovae using continuum subtracted H$\alpha$ images. We use the pixel statistics technique, normalised cumulative ranking (NCR), to associate SN pixels with H$\alpha$ emission. We find that our 77 SNe\,IIn do not follow the H$\alpha$ emission. This is not consistent with the proposed progenitors of SNe\,IIn, luminous blue variables (LBVs) as LBVs are high mass stars that undergo dramatic episodic mass loss. However, a subset of the NCR values follow the H$\alpha$ emission, suggesting a population of high mass progenitors. This suggests there may be multiple progenitor paths with $\sim$60\% having non-zero NCR values with a distribution consistent with high mass progenitors such as LBVs and $\sim$40\% of these SNe not being associated with H$\alpha$ emission. We discuss the possible progenitor routes of SNe\,IIn, especially for the zero NCR value population. We also investigate the radial distribution of the SNe in their hosts in terms of H$\alpha$ and $r'$-band flux.