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

¹ Institut für Astronomie, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
² Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
³ School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK

^a e-mail: farzana.meru@phys.ethz.ch

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 suciently 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.