The Evolution of Disk Winds from a Combined Study of Optical and Infrared Forbidden Lines

We analyze high-resolution (Δv ≤ 10 km s−1) optical and infrared spectra covering the [O i] λ6300 and [Ne ii] 12.81 μm lines from a sample of 31 disks in different evolutionary stages. Following work at optical wavelengths, we use Gaussian profiles to fit the [Ne ii] lines and classify them into high-velocity component (HVC) or low-velocity component (LVC) if the line centroid is more or less blueshifted than 30 km s−1 with respect to the stellar radial velocity, respectively. Unlike for the [O i], where an HVC is often accompanied by an LVC, all 17 sources with an [Ne ii] detection have either an HVC or an LVC. [Ne ii] HVCs are preferentially detected toward high accretors ( M⊙ yr−1), while LVCs are found in sources with low , low [O i] luminosity, and large infrared spectral index (n13–31). Interestingly, the [Ne ii] and [O i] LVC luminosities display an opposite behavior with n13–31: as the inner dust disk depletes (higher n13–31), the [Ne ii] luminosity increases while the [O i] weakens. The [Ne ii] and [O i] HVC profiles are generally similar, with centroids and FWHMs showing the expected behavior from shocked gas in microjets. In contrast, the [Ne ii] LVC profiles are typically more blueshifted and narrower than the [O i] profiles. The FWHM and centroid versus disk inclination suggest that the [Ne ii] LVC predominantly traces unbound gas from a slow, wide-angle wind that has not lost completely the Keplerian signature from its launching region. We sketch an evolutionary scenario that could explain the combined [O i] and [Ne ii] results and includes screening of hard (∼1 keV) X-rays in inner, mostly molecular, MHD winds.