The effect of radiative feedback on disc fragmentation

TL;DR

This study uses radiative hydrodynamic simulations to explore how radiative feedback from secondary objects influences disc fragmentation, revealing that feedback stabilizes discs and affects the formation and final masses of planets, brown dwarfs, and low-mass stars.

Contribution

It provides new insights into the role of radiative feedback in disc fragmentation, especially comparing continuous and episodic feedback effects on secondary object formation.

Findings

Continuous feedback stabilizes discs and reduces secondary object formation.

Episodic feedback temporarily stabilizes discs during outbursts, but they fragment again afterward.

Fragmented objects range from a few Jupiter masses to 0.1 solar masses.

Abstract

Protostellar discs may become massive enough to fragment producing secondary low-mass objects: planets, brown dwarfs and low-mass stars. We study the effect of radiative feedback from such newly-formed secondary objects using radiative hydrodynamic simulations. We compare the results of simulations without any radiative feedback from secondary objects with those where two types of radiative feedback are considered: (i) continuous, and (ii) episodic. We find that: (i) continuous radiative feedback stabilizes the disc and suppresses further fragmentation, reducing the number secondary objects formed; (ii) episodic feedback from secondary objects heats and stabilises the disc when the outburst occurs, but shortly after the outburst stops, the disc becomes unstable and fragments again. However, fewer secondary objects are formed compared to the the case without radiative feedback. We also find that the mass growth of secondary objects is mildly suppressed due to the effect of their radiative feedback. However, their mass growth also depends on where they form in the disc and on their subsequent interactions, such that their final masses are not drastically different from the case without radiative feedback. We find that the masses of secondary objects formed by disc fragmentation are from a few M$_{\rm J}$ to a few 0.1 M$_{\odot}$. Planets formed by fragmentation tend to be ejected from the disc. We conclude that planetary-mass objects on wide orbits (wide-orbit planets) are unlikely to form by disc fragmentation. Nevertheless, disc fragmentation may be a significant source of free-floating planets and brown dwarfs.