© Manuel Güdel

DG Tau is a single, nearby Young Stellar Object young enough to combine features common to embedded protostars and more evolved, optically revealed classical T Tauri stars. This transition object is therefore a key target to understand stellar accretion and ejection processes. It features a Keplerian disk with a hot, water-rich and strongly variable inner region, relics of a non-Keplerian envelope, accretion streamers, and most prominently a system of co-axial molecular, atomic, and ionized disk winds over a wide range of temperatures and velocities. The most extreme winds form a high-velocity bipolar jet system detected almost down to the disk surface at radio, infrared, optical, UV and surprisingly even X-ray wavelengths.

New JWST/MIRI observations reveal molecular lines of hot water and CO associated with the innermost protoplanetary disk; also, despite DG Tau’s youth, a substantial fraction of dust has grown to micron size. The jet system shows very strong infrared forbidden lines for which I will propose a direct link to the ~4 MK X-ray emitting plasma jet via shock heating and cooling. If successful, such a model will reveal more about the inner workings of the jet.

I will discuss shock models that involve collisional ionization and photoionization, shock self-radiation, recombination and charge exchange that are necessarily evolving away from collisional ionization equilibrium and therefore need to be evolved iteratively in time; I will address some diagnostic power of these models.