Directly probing the turbulent and thermal conditions of protoplanetary disks through molecular line emission. (remote)

ALMA gas observations of moderately inclined protoplanetary disks at sufficient resolution allow us to directly trace the emission location of various molecules in 3D. Through this innovative analysis it is possible to study the disk structure azimuthally, radially and vertically. In particular, the study of molecules linked to temperature, density and radiation conditions can be used to probe the disk physical properties such as turbulence.

This work presents observational results for the determination of the vertical distribution in CO isotopologues, HCN, CN, H2CO, HCO+, C2H in a sample of disks. From the CO isotopologue vertical profile it is posible to infer the gas pressure scale height of a disk and use optically thick tracers as a probe for the thermal structure. In some cases the CO emission surface shows perturbations that are correlated with gaps in the millimetre continuum and kinematical features. Other tracers, such as CN, give us information on the UV radiation affecting the disk material and through the location of H2CO we may be tracing different formation pathways.

Most excitingly, by connecting the information on the vertical and thermal structure at a particular disk region, we can directly resolve radial and vertical turbulence measurements. Constraining turbulence in disks is key towards understanding their evolution through the transport of angular momentum and bridging the timeline between protoplanetary disks and mature exoplanets. Our work presents empirical evidence for vertical gradients in turbulence which opens the discussion for ongoing instabilities such as MRI in these sources.

Overall, the study of moderately inclined disks opens an exciting avenue of research, deepening our understanding on the conditions and processes surrounding planet formation.