First release of high-redshift superluminous supernovae from the Subaru HIgh-Z sUpernova CAmpaign (SHIZUCA). I. Photometric properties

TL;DR

This paper reports the discovery and photometric analysis of high-redshift superluminous supernovae using Subaru's Hyper Suprime-Cam, providing initial estimates of their occurrence rates at redshifts 2 to 4.

Contribution

First detection and characterization of high-redshift superluminous supernovae from the SHIZUCA survey, demonstrating Hyper Suprime-Cam's effectiveness in high-z transient discovery.

Findings

Discovered three supernovae at z ~ 2 with magnitudes near -21 mag.

Estimated superluminous supernova rates at z ~ 2, 3, and 4.

Confirmed the capability of Hyper Suprime-Cam for high-redshift supernova surveys.

Abstract

We report our first discoveries of high-redshift supernovae from the Subaru HIgh-Z sUpernova CAmpaign (SHIZUCA), the transient survey using Subaru/Hyper Suprime-Cam. We report the discovery of three supernovae at the spectroscopically-confirmed redshifts of 2.399 (HSC16adga), 1.965 (HSC17auzg), and 1.851 (HSC17dbpf), and two supernova candidates with the host-galaxy photometric redshifts of 3.2 (HSC16apuo) and 4.2 (HSC17dsid), respectively. In this paper, we present their photometric properties and the spectroscopic properties of the confirmed high-redshift supernovae are presented in the accompanying paper (Curtin et al. 2019). The supernovae with the confirmed redshifts of z ~ 2 have the rest ultraviolet peak magnitudes close to -21 mag and they are likely superluminous supernovae. The discovery of three supernovae at z ~ 2 roughly corresponds to the approximate event rate of ~ 900 +/- 520 Gpc-3 yr-1 with Poisson error, which is consistent with the total superluminous supernova rate estimated by extrapolating the local rate based on the cosmic star-formation history. Adding unconfirmed superluminous supernova candidates would increase the event rate. Our superluminous supernova candidates at the redshifts of around 3 and 4 indicate the approximate superluminous supernova rates of ~ 400 +/- 400 Gpc-3 yr-1 (z ~ 3) and ~ 500 +/- 500 Gpc-3 yr-1 (z ~ 4) with Poisson errors. Our initial results demonstrate the outstanding capability of Hyper Suprime-Cam to discover high-redshift supernovae.