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

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 SNeIIn using continuum subtracted H alpha images. We use the pixel statistics technique, normalized 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 similar to 60 per cent having non-zero NCR values with a distribution consistent with high-mass progenitors such as LBVs and similar to 40 per cent 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.