Gas Accretion within the Dust Cavity in AB Aur

Area of Science:

• * Astronomy and Astrophysics
• * Protoplanetary Disk Studies
• * Astrochemistry

Background:

• * AB Aurigae (AB Aur) is a Herbig Ae star with a well-studied transitional disk.
• * Its proximity and low inclination make it ideal for investigating planet formation processes.
• * Transitional disks are key sites for observing planet formation.

Purpose of the Study:

• * To investigate the chemistry and dynamics of molecular gas in the AB Aur disk.
• * To understand the relationship between molecular gas and the observed mm continuum horseshoe structure.
• * To probe gas accretion mechanisms within the disk cavity.

Main Methods:

• * Utilized the NOEMA interferometer for high-angular-resolution mapping.
• * Observed the J = 3-2 rotational lines of HCO+ and HCN molecules.
• * Combined observations of HCO+ and HCN to analyze disk structure and chemistry.

Main Results:

• * Observed chemical segregation between HCO+ and HCN within the AB Aur disk.
• * HCO+ emission detected near the star, in a molecular bridge across the cavity, and in an outer ring.
• * HCN emission localized to an annular ring coincident with the dust ring, with a peak near a dust trap.

Conclusions:

• * The observed HCO+ bridge indicates gas accretion from the outer disk to the inner disk/jet system.
• * This finding provides evidence for gas accretion through the disk cavity, a critical step in planet formation.
• * Chemical segregation offers insights into the complex processes occurring in transitional disks.