The active young protostar DG Tau has an extended jet that has been well studied at radio , optical , and X-ray wavelengths .
We report sensitive new VLA full-polarization observations of the core and jet between 5 GHz and 8 GHz .
Our high angular resolution observation at 8 GHz clearly shows an unpolarized inner jet with a size 42 AU ( 0.35″ ) extending along a position angle similar to the optical-X ray outer jet .
Using our nearly coeval 2012 VLA observations , we find a spectral index \alpha = +0.46 \pm 0.05 , which combined with the lack of polarization , is consistent with bremsstrahlung ( free-free ) emission , with no evidence for a non-thermal coronal component .
By identifying the end of the radio jet as the optical depth unity surface , and calculating the resulting emission measure , we find our radio results are in agreement with previous optical line studies of electron density and consequent mass-loss rate .
We also detect a weak radio knot at 5 GHz located 7″ from the base of the jet , coincident with the inner radio knot detected by in 2009 but at lower surface brightness .
We interpret this as due to expansion of post-shock ionized gas in the three years between observations .