The Discovery of the Most Distant Known Type Ia Supernova at Redshift 1.914

TL;DR

This paper reports the discovery of the most distant Type Ia supernova at redshift 1.914 using Hubble Space Telescope data, providing insights into high-redshift supernova classification and cosmology.

Contribution

It presents the first detection and classification of a supernova at this redshift, demonstrating the effectiveness of combined spectral and photometric methods for high-redshift SN analysis.

Findings

First high-redshift (z=1.914) Type Ia supernova discovery.

Spectral data can often rule out SNe II but not always distinguish SNe Ia from SNe Ib/c.

Photometric and spectroscopic methods aid in supernova classification at high redshift.

Abstract

We present the discovery of a Type Ia supernova (SN) at redshift $z = 1.914$ from the CANDELS multi-cycle treasury program on the \textit{Hubble Space Telescope (HST)}. This SN was discovered in the infrared using the Wide-Field Camera 3, and it is the highest-redshift Type Ia SN yet observed. We classify this object as a SN\,Ia by comparing its light curve and spectrum with those of a large sample of Type Ia and core-collapse supernovae (SNe). Its apparent magnitude is consistent with that expected from the $\Lambda$CDM concordance cosmology. We discuss the use of spectral evidence for classification of $z > 1.5$ SNe\,Ia using {\it HST} grism simulations, finding that spectral data alone can frequently rule out SNe\,II, but distinguishing between SNe\,Ia and SNe\,Ib/c can require prohibitively long exposures. In such cases, a quantitative analysis of the light curve may be necessary for classification. Our photometric and spectroscopic classification methods can aid the determination of SN rates and cosmological parameters from the full high-redshift CANDELS SN sample.