Detecting z > 2 Type IIn Supernovae

TL;DR

This paper demonstrates that current optical surveys can effectively detect and confirm high-redshift (z > 2) Type IIn supernovae through their bright emission lines and color-selection techniques, enabling future large-scale searches.

Contribution

It introduces a method leveraging existing optical survey capabilities and galaxy color-selection to identify and spectroscopically confirm z > 2 SNe IIn efficiently.

Findings

Detectability of z > 2 SNe IIn in optical surveys.

Spectroscopic confirmation feasible with 8m-class telescopes.

High detection rate of Ly-alpha emission features in SNe IIn.

Abstract

Type IIn supernovae (SNe IIn) dominate the brightest supernova events in observed FUV flux (~1200-2000A). We show that multi-band, multi-epoch optical surveys complete to m_r = 27 can detect the FUV emission of ~25 z > 2 SNe IIn deg^-2 yr^-1 rest-frame (~10 SNe IIn deg^-2 yr^-1 observed-frame) to 4 sigma using a technique monitoring color-selected galaxies. Moreover, the strength and evolution of the bright emission lines observed in low redshift SNe IIn imply that the Ly-a emission features in ~70% of z > 2 SNe IIn are above 8m-class telescope spectroscopic thresholds for ~2 yr rest-frame. As a result, existing facilities have the capability to both photometrically detect and spectroscopically confirm z > 2 SNe IIn and pave the way for efficient searches by future 8m-class survey and 30m-class telescopes. The method presented here uses the sensitivities and wide-field capabilities of current optical instruments and exploits (1) the efficiency of z > 2 galaxy color-selection techniques, (2) the intrinsic brightness distribution (<M_B> = -19.0 +/-0.9) and blue profile of SNe IIn continua, (3) the presence of extremely bright, long-lived emission features, and (4) the potential to detect blueshifted SNe Ly-a emission shortward of host galaxy Ly-a features.