GIARPS links for the first time atomic and molecular winds in proto-planetary disks

Disk winds play a fundamental role in the evolution of protoplanetary systems. They are responsible for gas dissipation in the inner disk region by altering the disk surface density and eventually affecting the process that leads to the formation and migration of protoplanets. The complex structure and dynamics of disk winds can be investigated through the emission of atomic and molecular lines detected in high-resolution optical/infrared spectra of young stellar objects. Despite their great importance, however, studies connecting the atomic and molecular components are lacking so far. The GIARPS instrument, with its unique combination of high spectral resolution and wavelength coverage, is the ideal observing mode to perform this kind of investigation.

The GHOsT (GIARPS High-resolution Observations of T Tauri stars, P.I. S. Antoniucci, OAR) project, which we are currently carrying on, aims at determining for the first time in a statistically significant, homogeneous, and self-consistent way, stellar parameters and accretion/ejection properties of T Tauri stars with the use of the GIARPS instrument at TNG. The observed sample comprises young stars of the Taurus-Auriga star-forming region, covering a wide range of masses, mass accretion rates, and disk properties.

A first work of the GHOsT project (Giannini et al. 2019) has addressed the kinematic and physical properties of the jets and winds in a limited sample of six sources. In this work (Gangi et al. 2020), we study the relation between the atomic and molecular emission in 36 Classical T Tauri Stars (CTTs), focusing on a statistical analysis of the kinematic properties of the [OI] 630 nm and H2 2.12 μm lines and their mutual relation.

The [OI] line presents the typical composite profile, where components at different velocities can be identified, while the H2 line (with a detection rate of 50%) is in most cases single peaked and only slightly blueshifted, which is the signature of the origin in a slow disk wind. We highlight for the first time the kinematical link among the narrow low-velocity components of the H2 and [OI] emission, with a strong correlation between the peak velocities and the full widths at half maximum. Our results suggest that molecular and neutral atomic emission in disk winds originate from partially overlapping regions, and that the survival of molecular winds in disks strongly depends on the gas exposure to the radiation from the central star. This work highlights the importance of linking different tracers of the same phenomenon for a full comprehension of the mechanisms bringing to the disk dissipation. This is now possible thanks to the unique potential of GIARPS for this kind of observation!

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Example of continuum-subtracted [OI] and H2 line profiles (black lines). In red we plot the fit to the profiles, while single Gaussian components are shown as dashed blue lines. Image adapted from Gangi et al. 2020.

Link to the paper: Gangi et al., A&A,