GIARPS High-resolution Observations of T Tauri stars (GHOST) V. New insights into disk winds from 3 km/s resolution observations

This paper aims at revisit the physical and dynamical properties of the warm atomic gas in the inner disk region of classical T Tauri stars (CTTs) and relate them to the properties of the outer dusty disk. We used the high resolution (R=115,000) spectra of 36 CTTs observed as part of the GHOsT project and analysed the profile and luminosity of the brightest optical forbidden lines, namely [OI]630 and 557nm, [SII]406 and 673nm, and [NII]658nm. We find that in about 40% of sources the so-called narrow low-velocity component (NLVC) display a peak velocity compatible with the stellar velocity. In these sources, that typically show lower mass accretion rates and the absence of a jet, the [OI]630nm profiles are well fitted by a simple Keplerian disk model, indicating that the emission from the disk is dominant with respect to the wind contribution. For transitional disks (TD), no correlation is found between $R_{kep}$, derived from the line HWHM, and the size of the dust cavity. We also see an anti-correlation between the [OI] 557/630 nm ratio and $R_{kep}$, which suggests that the [OI] emitting region expands as the gas cools and becomes less dense. We confirmed previous findings on the density and temperature ranges implied by the line ratios, and additionally constrained the ionisation fraction in the NLVC to be < 0.1. We however discuss the limits of applying this diagnostic to winds that are not spatially resolved. For the outflow component, we estimated the mass-loss for both the disk winds and jets and compared the results with X-ray photoevaporative models. We conclude that without better knowledge of the wind geometry, and given the limitation of the diagnostics, the mass-loss in the wind traced by the LVC cannot be constrained better than a factor of 100, with a mass-loss/mass-accretion ratio spanning between ~ 0.01 and more than 1.