Subarcsecond high-sensitivity measurements of the DG Tau jet with e-MERLIN

We present very high spatial resolution deep radio continuum observations at 5 GHz (6 cm) made with the extended Multi-Element Radio Linked Interferometer Network (e-MERLIN) of the young stars DG Tau A and B. Assuming it is launched very close (≃1 au) from the star, our results suggest that the DG Tau A outflow initially starts as a poorly focused wind and undergoes significant collimation farther along the jet (≃50 au). We derive jet parameters for DG Tau A and find an initial jet opening angle of 86° within 2 au of the source, a mass-loss rate of 1.5 × 10−8 M⊙ yr−1 for the ionized component of the jet, and the total ejection-to-accretion ratio to range from 0.06 to 0.3. These results are in line with predictions from magnetohydrodynamic jet-launching theories.