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Recent studies have revealed intense UV metal emission lines in a modestsample of z>7 Lyman-alpha emitters, indicating a hard ionizing spectrum ispresent. If such high ionization features are shown to be common, it mayindicate that extreme radiation fields play a role in regulating the visibilityof Lyman-alpha in the reionization era. Here we present deep near-infraredspectra of seven galaxies with Lyman-alpha emission at 5.4<z<8.7 (including anewly-confirmed lensed galaxy at z=6.031) and three bright z>7 photometrictargets. In nine sources we do not detect UV metal lines. However in thez=8.683 galaxy EGSY8p7, we detect a 4.6 sigma emission line in the narrowspectral window expected for NV 1243. The feature is unresolved (FWHM<90 km/s)and is likely nebular in origin. A deep H-band spectrum of EGSY8p7 revealsnon-detections of CIV, He II, and OIII]. The presence of NV requires asubstantial flux of photons above 77 eV, pointing to a hard ionizing spectrumpowered by an AGN or fast radiative shocks. Regardless of its origin, theintense radiation field of EGSY8p7 may aid the transmission of Lyman-alphathrough what is likely a partially neutral IGM. With this new detection, fiveof thirteen known Lyman-alpha emitters at z>7 have now been shown to haveintense UV line emission, suggesting that extreme radiation fields arecommonplace among the Lyman-alpha population. Future observations with JWSTwill eventually clarify the origin of these features and explain their role inthe visibility of Lyman-alpha in the reionization era.

Spectroscopic Constraints on UV Metal Line Emission at z~6-9: The Nature of Lyman-alpha Emitting Galaxies in the Reionization-Era