# Gas accretion within the dust cavity in AB Aur

## TL;DR

This study uses high-resolution molecular line observations to reveal chemical segregation and gas accretion flows within the dust cavity of the AB Aur disk, shedding light on planet formation processes.

## Contribution

It provides the first detailed mapping of molecular gas dynamics and chemistry inside the dust cavity of AB Aur, demonstrating gas accretion through the cavity.

## Key findings

- HCO+ shows intense emission at the star and a bright bridge indicating accretion.
- HCO+ and HCN distributions reveal chemical segregation in the disk.
- Evidence of gas flow from the outer ring to the inner disk via the dust cavity.

## Abstract

AB Aur is a Herbig Ae star hosting a well-known transitional disk. Because of its proximity and low inclination angle, it is an excellent object to study planet formation. Our goal is to investigate the chemistry and dynamics of the molecular gas component in the AB Aur disk, and its relation with the prominent horseshoe shape observed in continuum mm emission. We used the NOEMA interferometer to map with high angular resolution the J = 3-2 lines of HCO+ and HCN. By combining both, we can gain insight into the AB Aur disk structure. Chemical segregation is observed in the AB Aur disk: HCO+ shows intense emission toward the star position, at least one bright molecular bridge within the dust cavity, and ring-like emission at larger radii, while HCN is only detected in an annular ring that is coincident with the dust ring and presents an intense peak close to the dust trap. We use HCO+ to investigate the gas dynamics inside the cavity. The observed bright HCO+ bridge connects the compact central source with the outer dusty ring. This bridge can be interpreted as an accretion flow from the outer ring to the inner disk/jet system proving gas accretion through the cavity.