Spectroscopic Confirmation Of An Extreme Starburst At Redshift 4.547
  We report the spectroscopic confirmation of a sub-mm galaxy (SMG) at z=4.547 with an estimated L_IR=0.5-2.0x10^13 L_sun. The spectra, mid-IR, and X-ray properties indicate the bolometric luminosity is dominated by star formation at a rate of >1000M_sun per yr. Multiple, spatially separated components are visible in the Ly-Alpha line with an observed velocity difference of up to 380 km/sec 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 >10^10 M_sun of stellar mass. This object is a likely progenitor for the massive early type systems seen at z~2. 
Peter Capak, C. L. Carilli, N. Lee, T. Aldcroft, H. Aussel, E.   Schinnerer, G.W. Wilson, M. S. Yun, A . Blain, M. Giavalisc...