Triggered fragmentation in gravitationally unstable discs: forming fragments at small radii

TL;DR

This study uses 3D radiation hydrodynamical simulations to investigate how gravitationally unstable discs fragment and how this process influences mass movement and potential subsequent fragmentation at smaller radii.

Contribution

It reveals the dynamic behavior of fragmented discs, showing increased radial velocities and the possibility of inner disc fragmentation triggered by outer disc events.

Findings

Radial velocity increases by 2-3 times after fragmentation.

Inward mass flow can lead to dense inner spirals.

Inner disc regions may fragment following outer disc fragmentation.

Abstract

We carry out three dimensional radiation hydrodynamical simulations of gravitationally unstable discs using to explore the movement of mass in a disc following its fragmentation. Compared to a more quiescent state before it fragments, the radial velocity of the gas increases by up to a factor of ~2-3 after fragmentation. While the mass movement occurs both inwards and outwards, the inwards motion can cause the inner spirals to be sufficiently dense that they may become unstable and potentially fragment. Consequently, the dynamical behaviour of fragmented discs may cause subsequent fragmentation at smaller radii after an initial fragment has formed in the outer disc.