Detection of two massive CO systems in 4C 41.17 at z = 3.8

We have detected CO(4-3) in the $z=3.8$ radio galaxy 4C 41.17 with the IRAM Interferometer. The CO is in two massive ($M_{\rm dyn} \sim 6 \times 10^{10}~M_{\odot}$) systems separated by 1$\farcs$8 (13 kpc), and by 400${\rm\,km\,s^{-1}}$ in velocity, which coincide with two different dark lanes in a deep Lyα image. One CO component coincides with the cm-radio core of the radio galaxy, and its redshift is close to that of the $\ion{He}{ii}$ λ 1640 AGN line. The second CO component is near the base of a cone-shaped region southwest of the nucleus, which resembles the emission-line cones seen in nearby AGN and starburst galaxies. The characteristics of the CO sources and their mm/submm dust continuum are similar to those found in ultraluminous IR galaxies and in some high-z radio galaxies and quasars. The fact that 4C 41.17 contains two CO systems is further evidence for the role of mergers in the evolution of galaxies at high redshift.