First release of high-redshift superluminous supernovae from the Subaru
  HIgh-Z sUpernova CAmpaign (SHIZUCA). II. Spectroscopic properties
  We present Keck spectroscopic observations of three probable high redshift
superluminous supernovae (SLSNe) from the Subaru HIgh-Z sUpernova CAmpaign
(SHIZUCA), confirming redshifts of 1.851, 1.965 and 2.399. The host galaxies
were selected for transient monitoring from multi-band photometric redshifts.
The supernovae are detected during their rise, and the classically scheduled
spectra are collected near maximum light. The restframe far-ultraviolet
(FUV;$\sim$1000A-2500A) spectra include a significant host galaxy flux
contribution and we compare our host galaxy subtracted spectra to UV-luminous
SNe from the literature. While the signal-to-noise ratios of the spectra
presented here are sufficient for redshift confirmation, supernova
spectroscopic type confirmation remains inconclusive. The success of the first
SHIZUCA Keck spectroscopic follow-up program demonstrates that campaigns such
as SHIZUCA are capable of identifying high redshift SLSNe with sufficient
accuracy, speed and depth for rapid, well-cadenced and informative follow-up.
