Evidence For A Vertical Dependence on the Pressure Structure in AS 209

TL;DR

This study introduces an improved method for measuring disk rotation curves, revealing pressure perturbations in AS 209 that influence the vertical structure and distribution of dust grains, with implications for understanding disk dynamics.

Contribution

The paper presents a new technique for analyzing non-axisymmetric rotation curves, uncovering pressure perturbations and their vertical dependence in the AS 209 protoplanetary disk.

Findings

Detected up to ±5% deviations from Keplerian rotation.

Identified pressure maxima coinciding with NIR rings.

Found radial offsets between NIR and mm continuum rings.

Abstract

We present an improved method to measure the rotation curves for disks with non-axisymmetric brightness profiles initially published in Teague et al. (2018a). Application of this method to the well studied AS$~$209 system shows substantial deviations from Keplerian rotation of up to $\pm 5\%$. These deviations are most likely due to perturbations in the gas pressure profile, including a perturbation located at $\approx 250~$au and spanning up to $\approx 50~$au which is only detected kinematically. Modelling the required temperature and density profiles required to recover the observed rotation curve we demonstrate that the rings observed in $\mu$m scattered light are coincident with the pressure maxima, and are radially offset from the rings observed in mm continuum emission. This suggests that if rings in the NIR are due to sub-$\mu$m grains trapped in pressure maxima that there is a vertical dependence on the radius of the pressure minima.