A spectroscopically confirmed, strongly lensed, metal-poor Type II supernova at z = 5.13

TL;DR

This paper reports the discovery and spectroscopic confirmation of a highly magnified, metal-poor Type II supernova at redshift 5.13, providing insights into early star formation and galaxy evolution in the Universe's first billion years.

Contribution

It presents the first spectroscopically confirmed supernova at z > 5, demonstrating the power of gravitational lensing and JWST observations to study early Universe stellar phenomena.

Findings

SN Eos is the farthest spectroscopically confirmed supernova.

Progenitor star formed in a metal-poor environment (<= 0.1 Z_{\odot}).

Lensing magnification enabled detection of this high-redshift supernova.

Abstract

Observing supernovae (SNe) in the early Universe (z > 3) provides a window into how both galaxies and individual stars have evolved over cosmic time, yet a detailed study of high-redshift stars and SNe has remained difficult due to their extreme distances and cosmological redshifting. To overcome the former, searches for gravitationally lensed sources allow for the discovery of magnified SNe that appear as multiple images - further providing the opportunity for efficient follow-up. Here we present the discovery of "SN Eos": a strongly lensed, multiply-imaged, SN II at a spectroscopic redshift of z = 5.133 +/- 0.001. SN Eos exploded in a Lyman-{\alpha} emitting galaxy when the Universe was only ~1 billion years old, shortly after it reionized and became transparent to ultraviolet radiation. A year prior to our discovery in JWST data, archival HST imaging of SN Eos reveals rest-frame far ultraviolet (~1,300{\AA}) emission, indicative of shock breakout or interaction with circumstellar material in the first few (rest-frame) days after explosion. The JWST spectroscopy of SN Eos, now the farthest spectroscopically confirmed SN ever discovered, shows that SN Eos's progenitor star likely formed in a metal-poor environment (<= 0.1 Z_{\odot}), providing the first direct evidence of massive star formation in the metal-poor, early Universe. SN Eos would not have been detectable without the extreme lensing magnification of the system, highlighting the potential of such discoveries to eventually place constraints on the faint end of the cosmic star-formation rate density in the very early Universe.