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 ^ { \prime } _ { CO } = ( 8.7 \pm 0.8 ) \times 10 ^ { 10 } K km s ^ { -1 } pc ^ { 2 } and L ^ { \prime } _ { CO } = ( 6.0 \pm 0.5 ) \times 10 ^ { 10 } K km s ^ { -1 } 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 \sim 9 \times 10 ^ { 10 } M _ { \odot } .
In BRI1335-0417 we measure L ^ { \prime } _ { CO } = ( 7.3 \pm 0.6 ) \times 10 ^ { 10 } K km s ^ { -1 } pc ^ { 2 } .
We detect continuum emission in the SMG BR1202-0725 North ( S _ { 44 GHz } = 51 \pm 6 \mu Jy ) , while the quasar is detected with S _ { 44 GHz } = 24 \pm 6 \mu Jy and in BRI1335-0417 we measure S _ { 44 GHz } = 40 \pm 7 \mu Jy .
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 % .