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

Abstract

We analyze high-resolution (Delta v <= 10 km s(-1)) optical and infrared spectra covering the [O i] lambda 6300 and [Ne II] 12.81 mu m 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) over dot(ace) > 10(-8) M-circle dot yr(-1)), while LVCs are found In sources with low M-acc, low [O I] luminosity, and large Infrared spectral Index (n(13-31)). Interestingly, the [Ne II] and [O I] LVC luminosities display an opposite behavior with n(13-31): as the Inner dust disk depletes (higher n(13-31)), 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 (similar to 1 keV) X-rays In Inner, mostly molecular, MHD winds.