Karl G. Jansky Very Large Array observations of cold dust and molecular
  gas in starbursting quasar host galaxies at z~4.5
  We present Karl G. Jansky Very Large Array (VLA) observations of 44 GHz
continuum and CO J=2-1 line emission in BR1202-0725 at z=4.7 (a starburst
galaxy and quasar pair) and BRI1335-0417 at z=4.4 (also hosting a quasar). With
the full 8 GHz bandwidth capabilities of the upgraded VLA, we study the
(rest-frame) 250 GHz thermal dust continuum emission for the first time along
with the cold molecular gas traced by the Low-J CO line emission. The measured
CO J=2-1 line luminosities of BR1202-0725 are L'(CO) = (8.7+/-0.8)x10^10 K km/s
pc^2 and L'(CO) = (6.0+/-0.5)x10^10 K km/s pc^2 for the submm galaxy (SMG) and
quasar, which are equal to previous measurements of the CO J=5-4 line
luminosities implying thermalized line emission and we estimate a combined cold
molecular gas mass of ~9x10^10 Msun. In BRI1335-0417 we measure L'(CO) =
(7.3+/-0.6)x10^10 K km/s pc^2. We detect continuum emission in the SMG
BR1202-0725 North (S(44GHz) = 51+/-6 microJy), while the quasar is detected
with S(44GHz) = 24+/-6 microJy and in BRI1335-0417 we measure S(44GHz) = 40+/-7
microJy. Combining our continuum observations with previous data at
(rest-frame) far-infrared and cm-wavelengths, we fit three component models in
order to estimate the star-formation rates. This spectral energy distribution
fitting suggests that the dominant contribution to the observed 44~GHz
continuum is thermal dust emission, while either thermal free-free or
synchrotron emission contributes less than 30%.
