Previous abstract Next abstract
We propose that the thermal radio continuum and the hydrogen near infrared line emission measured in many young stellar objects can be produced in an accretion disk-driven hydromagnetic wind. Previously, the interpretation of these emission signatures in low-mass protostars in terms of ordinary stellar winds and standard photoionization models led to difficulties such as the line excess problem. In the context of disk-driven winds, high temperatures and ionization fractions can be established by ambipolar-diffusion heating at large distances from the protostar. We demonstrate that this hot zone can produce free-free emission at a level consistent with that detected in classical T Tauri stars. Also, by solving the full non-LTE rate equations, including velocity gradients, for hydrogen along the flow, we show that the heating is sufficient to collisionally populate the higher levels of hydrogen which give rise to the observed near infrared lines. We discuss the radio continuum morphologies, luminosities, and spectra (between 1 and 20 GHz) as well as the hydrogen line luminosities (including Br$\alpha$ and Br$\gamma$) predicted by our models and compare them with the observations.
Friday program listing