A reaction-diffusion model for describing the ring/gap structure in disks surrounding individual young stars

TL;DR

This paper proposes a reaction-diffusion model with a moving reaction front to explain the evolution of disk structures around young stars, linking observed ring-gap features to chemical and physical processes during star formation.

Contribution

It introduces a novel application of reaction-diffusion systems with moving reaction fronts to classify and understand protostellar disk structures based on observational data.

Findings

Protostar-disk systems resemble reaction-diffusion compartments.

Outflows act as moving reaction fronts triggering molecular formation.

Disk evolution from continuous to ring-gap structures is linked to the passage of the reaction front.

Abstract

The embedded disks surrounding individual Class 0 protostars are structureless. Disks surrounding Class I stars may be continuous or have a ring-gap substructure, whereas all disks around Class II stars have a ring-gap substructure that gradually disappear as the disks evolve into debris disks. This common sequence in young lone stars requires an explanation. This study aims to show that the physical model Reaction-Diffusion Systems with Moving Reaction Front can be used to describe and classify protostellar disks according to their structure. A comprehensive review of observations made with the ALMA radio telescope shows: first, that the protostar-disk system presents a geometry analogous to that of an reaction-diffusion system with two separate compartments, namely, protostar and disk. Second, that in the protostar, matter is processed at high temperature, resulting in a chemical composition different from that of the disk. Third, that the equatorial outflow emitted by the protostar, rich in highly reactive trihydrogen cation, acts as a moving reaction front, MRF, that triggers the formation of molecules and nuclei in the disk. The time lag of nucleation with respect to the passage of the MRf would be the cause of the formation of the gaps between the rings of particles that form in the disk. The MRF is a transient phenomenon and its passage causes the transformation of a continuous disk, Class 0, into a disk with a ring-gap structure, Class II, whose temporal evolution begins at the interface of the star and moves outwards.