Observing the linked depletion of dust and CO gas at 0.1-10 au in disks of intermediate-mass stars

TL;DR

This study uncovers a correlation between dust and CO gas depletion in the inner regions of disks around intermediate-mass stars, revealing how dust is being depleted as CO gas emission moves outward, with implications for understanding disk evolution.

Contribution

It demonstrates a linked depletion of dust and CO gas in the inner disks of intermediate-mass stars, providing new insights into disk dispersal processes.

Findings

Recession of CO emission correlates with dust depletion in disks.

Herbig disk cavities show a bimodal near-infrared excess.

Inner disk dust depletion is linked to CO gas distribution.

Abstract

We report on the discovery of correlations between dust and CO gas tracers of the 0.1-10 au region in planet-forming disks around young intermediate-mass stars. The abundance of refractory elements on stellar photospheres decreases as the location of hot CO gas emission recedes to larger disk radii, and as the near-infrared excess emission from hot dust in the inner disk decreases. The linked behavior between these observables demonstrates that the recession of infrared CO emission to larger disk radii traces an inner disk region where dust is being depleted. We also find that Herbig disk cavities have either low (~ 5-10 %) or high (~ 20-35 %) near-infrared excess, a dichotomy that has not been captured by the classic definition of "pre-transitional" disks.