Context : Models of the young solar nebula assume a hot initial disk such that most volatiles are in the gas phase .
Water emission arising from within 50 AU radius has been detected around low-mass embedded young stellar objects .
The question remains whether an actively accreting disk is warm enough to have gas-phase water up to 50 AU radius .
No detailed studies have yet been performed on the extent of snowlines in an accreting disk embedded in a dense envelope ( Stage 0 ) .

Aims : Quantify the location of gas-phase volatiles in the inner envelope and disk system for an actively accreting embedded disk .

Methods : Two-dimensional physical and radiative transfer models have been used to calculate the temperature structure of embedded protostellar systems .
The heating due to viscous accretion is added through the diffusion approximation .
Gas and ice abundances of H _ { 2 } O , CO _ { 2 } , and CO are calculated using the density dependent thermal desorption formulation .

Results : The midplane water snowline increases from 3 to \sim 55 AU for accretion rates through the disk onto the star between 10 ^ { -9 } – 10 ^ { -4 } M _ { \odot } { yr ^ { -1 } } .
CO _ { 2 } can remain in the solid phase within the disk for \dot { M } \leq 10 ^ { -5 } M _ { \odot } { yr ^ { -1 } } down to \sim 20 AU .
Most of the CO is in the gas phase within an actively accreting disk independent of disk properties and accretion rate .
The predicted optically thin water isotopolog emission is consistent with the detected H _ { 2 } ^ { 18 } O emission toward the Stage 0 embedded young stellar objects , originating from both the disk and the warm inner envelope ( hot core ) .
An accreting embedded disk can only account for water emission arising from R < 50 AU , however , and the extent rapidly decreases for \dot { M } \leq 10 ^ { -5 } M _ { \odot } { yr ^ { -1 } } .
Thus , the radial extent of the emission can be measured with future ALMA observations and compared to this 50 AU limit .

Conclusions : Volatiles such as H _ { 2 } O , CO _ { 2 } , CO , and the associated complex organics sublimate out to 50 AU in the midplane of young disks and , thus , can reset the chemical content inherited from the envelope in periods of high accretion rates ( > 10 ^ { -5 } M _ { \odot } { yr ^ { -1 } } ) .
A hot young solar nebula out to 30 AU can only have occurred during the deeply embedded Stage 0 , not during the T Tauri phase of our early solar system .