SN 2010jl in UGC 5189: Yet another luminous type IIn supernova in a metal-poor galaxy

TL;DR

This paper reports on the luminous type IIn supernova SN 2010jl in a low-metallicity galaxy, highlighting the correlation between supernova luminosity and host galaxy metallicity, and discussing implications for stellar evolution in the early universe.

Contribution

It provides detailed observations of SN 2010jl, compares its properties with other luminous supernovae, and emphasizes the trend of high luminosity supernovae occurring in low-metallicity environments.

Findings

SN 2010jl is a luminous supernova with M_I ~ -20.5.

Luminous supernovae are predominantly found in low-metallicity galaxies.

Over-luminous core-collapse supernovae tend to occur in environments with low gas-phase oxygen abundance.

Abstract

We present ASAS data starting 25 days before the discovery of the recent type IIn SN 2010jl, and we compare its light curve to other luminous IIn SNe, showing that it is a luminous (M_I ~ -20.5) event. Its host galaxy, UGC 5189, has a low gas-phase oxygen abundance (12 + log(O/H) = 8.2), which reinforces the emerging trend that over-luminous core-collapse supernovae are found in the low-metallicity tail of the galaxy distribution, similar to the known trend for the hosts of long GRBs. We compile oxygen abundances from the literature and from our own observations of UGC 5189, and we present an unpublished spectrum of the luminous type Ic SN 2010gx that we use to estimate its host metallicity. We discuss these in the context of host metallicity trends for different classes of core-collapse objects. The earliest generations of stars are known to be enhanced in [O/Fe] relative to the Solar mixture; it is therefore likely that the stellar progenitors of these overluminous supernovae are even more iron-poor than they are oxygen-poor. A number of mechanisms and massive star progenitor systems have been proposed to explain the most luminous core-collapse supernovae; any successful theory will need to include the emerging trend that points towards low-metallicity for the massive progenitor stars. This trend for very luminous supernovae to strongly prefer low-metallicity galaxies should be taken into account when considering various aspects of the evolution of the metal-poor early universe. (abridged)