Photoevaporation Does Not Completely Empty Protoplanetary Disks
A new study using two-dimensional hydrodynamic simulations reveals that the photoevaporation process, driven by stellar light, is not capable of carving clean inner cavities in the gas and dust disks surrounding young stars. The results challenge previous theoretical models and offer a more complex view of how these planetary nurseries evolve. 🌌
Mechanisms That Prevent Total Emptying
The research couples the disk structure with the photoevaporative flow. When a depression in gas density begins, the local rate at which the disk loses mass decreases dramatically. This slows the deepening of the gap. Additionally, two key processes counteract the emptying:
Processes That Refill the Depression:- Inward Viscous Flow: Material from the outer disk slowly flows toward the lower density region.
- Radial Mass Transport: Along the disk surface, gas moves to partially refill the depleted zone.
- The combined action generates a persistent configuration that barely depends on the initial state of the disk.
The disk resists being emptied solely by the light of its star, preferring to maintain a thin veil of material.
Implications for Transition Disks
This behavior challenges the standard paradigm that directly linked photoevaporation to the creation of transition disks, which show apparently empty inner gaps. However, the study finds a crucial secondary effect: the pressure maximum at the edge of the depression can trap dust grains. This would produce infrared observational signatures very similar to those of a classic transition disk, complicating the interpretation of observations. 🔍
Advances for Modeling Evolution:- The researchers propose a first-order prescription to approximate this phenomenon in one-dimensional evolution models.
- This tool is suitable for use in studies simulating planet formation and synthesizing disk populations.
- Although it improves previous static treatments for calculating mass loss, it remains an approximation.
The Way Forward: Complex Simulations
The work underscores the urgent need to run more multidimensional simulations