An Hα survey of the host environments of 77 type IIn supernovae within z < 0.02

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 Hα emission and the progenitor masses of SN classes. In this paper, we present the largest environmental study of SNe IIn. We analyse the Hα environments of 77 type IIn supernovae using continuum subtracted Hα images. We use the pixel statistics technique, normalised cumulative ranking (NCR), to associate SN pixels with Hα emission. We find that our 77 SNe IIn do not follow the Hα 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 Hα emission, suggesting a population of high mass progenitors. This suggests there may be multiple progenitor paths with ∼60 per cent having non-zero NCR values with a distribution consistent with high mass progenitors such as LBVs and ∼40 per cent of these SNe not being associated with Hα 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 Hα and r′-band flux.