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

Abstract

We analyze high-resolution (∆v ≤ 10 km/s) optical and infrared spectra covering the [O I] 6300 Å 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 HVC (LVC) if the line centroid is more (less) blueshifted than 30 km/s with respect to the stellar radial velocity. Unlike for the [O I] where a HVC is often accompanied by a LVC, all 17 sources with a [Ne II] detection have either a HVC or a LVC. [Ne II] HVCs are preferentially detected toward high accretors ( Ṁacc > 10 −8 M /yr) while LVCs are found in sources with low Ṁacc , low [O I] luminosity, and large infrared spectral index (n 13−31 ). Interestingly, the [Ne II] and [O I] LVC luminosities display an opposite behaviour 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 behaviour from shocked gas in micro-jets. In contrast, the [Ne II] LVC profiles are typically more blueshifted and narrower than the [O I] profiles. The FWHM and centroid vs. disk inclination suggest that the [Ne II]LVC predominantly traces unbound gas from a slow, wideangle 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.

UV Fluorescence Traces Gas and LyA Evolution in Protoplanetary Disks

“…Trends in forbidden emission from [O I] and [Ne II] provide some insight into the Lyα profiles for this group of targets. Pascucci et al (2020) find that CS Cha, DM Tau, T Cha, UX Tau, and V4046 Sgr all have Simon et al 2016;Banzatti et al 2019;Pascucci et al 2020). Furthermore, none of the targets in this group show high velocity [O I] emission, implying that the jets and other high velocity outflows have turned off.…”

“…We expand on each of the three UV-CO categories in the following subsections. In particular, we investigate the connection between Lyα emission and the structure of the gas and dust disks, which appears analagous to the evolutionary sequence discovered in optical and infrared emission from forbidden lines in disk winds (see e.g., [O I], [Ne II];Banzatti et al 2019;Pascucci et al 2020).…”