Cosmic rate of type IIn supernovae and its evolution with redshift

Abstract

Context. Type IIn supernovae potentially constitute a large fraction of the gravitationally lensed supernovae predicted to be found with upcoming facilities. However, the local rate is used for these estimates, which is assumed to be independent of properties such as the host galaxy mass. Some studies hint that a host galaxy mass bias may exist for IIn supernovae. Aims. This paper aims to provide an updated local IIn supernova-to-core-collapse ratio based on data from the Palomar Transient Factory (PTF) and the Zwicky Transient Facility (ZTF) Bright Transient Survey (BTS). Furthermore, the goal is to investigate the dependency of the IIn supernova peak magnitude on the host galaxy mass and the consequences of a possible host galaxy mass preference on the volumetric rate of type IIn supernovae. Methods. We constructed approximately volume-limited subsamples to determine the local IIn supernova-to-core-collapse ratio. We investigated the absolute peak magnitude of a subsample of type IIn and superluminous II or IIn supernovae exploring how this relates to the i-band magnitude of the host galaxies (as a proxy for stellar mass). We presented a method to quantify the effect of a potential preference for low-mass host galaxies utilizing the UNIVERSEMACHINE algorithm. Results. The IIn supernova-to-core-collapse ratios for PTF and BTS are 0.046 ± 0.013 and 0.048 ± 0.011, respectively, which results in a ratio of 0.047 ± 0.009, which is consistent with the ratio of 0.05 currently used to estimate the number of gravitationally lensed IIn supernovae. We report fainter host galaxy median absolute magnitudes for type IIn brighter than −20.5 mag with a 3σ significance. If the IIn supernova-to-core-collapse ratio were described by the power law model IIn/CC = 0.15 × log(M/M⊙)−0.05, we would expect a slightly elevated volumetric rate for redshifts beyond 3.2.