NEW CONSTRAINTS ON THE MOLECULAR GAS IN THE PROTOTYPICAL HyLIRGs BRI 1202–0725 AND BRI 1335–0417

Abstract

We present Karl G Jansky Very Large Array observations of CO( ) line emission and rest-frame 250 GHz continuum emission of the Hyper-Luminous IR Galaxies (HyLIRGs) BRI 1202–0725 (z = 4.69) and BRI 1335–0417 (z = 4.41), with an angular resolution as high as 0.″15. Our low-order CO observations delineate the cool molecular gas, the fuel for star formation in the systems, in unprecedented detail. For BRI 1202–0725, line emission is seen from both extreme starburst galaxies: the quasar host and the optically obscured submm galaxy (SMG), in addition to one of the Lyα emitting galaxies in the group. Line emission from the SMG shows an east–west extension of about 0.″6. For Lyα-2, the CO emission is detected at the same velocity as [C ii] and [N ii], indicating a total gas mass ∼4.0 × 1010 M⊙. The CO emission from BRI 1335–0417 peaks at the nominal quasar position, with a prominent northern extension (∼1″, a possible tidal feature). The gas depletion timescales are ∼107 years for the three HyLIRGs, consistent with extreme starbursts, while that of Lyα-2 may be consistent with main sequence galaxies. We interpret these sources as major star formation episodes in the formation of massive galaxies and supermassive black holes via gas-rich mergers in the early universe.