Spectroscopic Confirmation of an Extreme Starburst at Redshift 4.547

We report the spectroscopic confirmation of a submillimeter galaxy (SMG) at -->z = 4.547 with an estimated LIR = (0.5-2.0) ? 1013 L?. The spectra, mid-IR, and X-ray properties indicate the bolometric luminosity is dominated by star formation at a rate of >1000 M? -->yr?1. Multiple, spatially separated components are visible in the Ly? line with an observed velocity difference of up to 380 km -->s?1 and the object morphology indicates a merger. The best-fit spectral energy distribution and spectral line indicators suggest the object is 2-8 Myr old and contains >1010 M? of stellar mass. This object is a likely progenitor for the massive early-type systems seen at -->z ~ 2.

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