Revealing the diversity of Type IIn supernova progenitors through their environments

TL;DR

This study uses high-resolution HST imaging to analyze the diverse environments of Type IIn supernovae, revealing a wide range of progenitor masses, evolutionary stages, and binary interaction histories.

Contribution

It provides new insights into the diversity of Type IIn supernova progenitors by classifying their environments and linking them to progenitor properties.

Findings

Bright SNe IIn occur in star-forming regions, indicating massive progenitors.

Faint SNe IIn are found in older environments, suggesting less massive progenitors.

Progenitors are brighter or bluer than their environments' stellar populations, implying binary interactions or non-quiescent states.

Abstract

Type IIn supernovae (SNe IIn) are hydrogen-rich explosions embedded in dense circumstellar medium (CSM), which gives rise to their characteristic narrow hydrogen emission lines. The nature of their progenitors and pre-explosion mass loss remains, however, poorly understood. Using high-resolution Hubble Space Telescope (HST) imaging, we analyze the local stellar environments of a volume-limited sample (z < 0.02) of 31 SNe IIn. The environments of SNe IIn are found to be very diverse; the SN could reside within a star-forming region (Class 1), outside a star-forming region (Class 2), or in much older environments without any obvious signs of star formation (Class 3). The bright SNe IIn (Mpeak < -19.5 mag) predominantly occur in Class 1 environments, indicative of very massive progenitors, while the faint SNe IIn (Mpeak < -15.5 mag) are associated with Classes 2 and 3 environments, suggesting the least massive progenitors. Meanwhile, normal SNe IIn with -19.5 < Mpeak < -15.5 mag occur in all three types of environments, suggesting a diversity in their progenitor mass, lifetime, and evolutionary pathways. Moreover, the directly detected SN IIn progenitors are systematically brighter and/or bluer than the youngest stellar populations in their environments, suggesting that they were either in a non-quiescent state when observed or had experienced binary interactions. These results point to a significantly diverse origin for progenitors of SNe IIn, spanning a wide range of masses, evolutionary stages, and potential binary interaction histories.