Formation of Jupiter-Mass Binary Objects through photoerosion of fragmenting cores

TL;DR

This paper proposes that the formation of Jupiter-mass binary objects in star-forming regions can be explained by photoerosion of prestellar cores by radiation from massive stars, accounting for their observed wide separations and masses.

Contribution

It introduces a novel mechanism of photoerosion to explain the origin and properties of free-floating Jupiter-mass binary objects in the Orion Nebula Cluster.

Findings

Photoerosion can produce substellar masses consistent with JuMBOs.

JuMBO separations match those of more massive binaries formed from core fragmentation.

Most JuMBOs are located outside HII regions, suggesting formation within and migration afterward.

Abstract

The recent discovery of tens of Jupiter-mass binary objects (JuMBOs) in the Orion Nebula Cluster with the James Webb Space Telescope has intensified the debate on the origin of free-floating planetary mass objects within star-forming regions. The JuMBOs have masses below the opacity limit for fragmentation, but have very wide separations (10s - 100s au), suggesting that they did not form in a similar manner to other substellar mass binaries. Here, we propose that the theory of photoerosion of prestellar cores by Lyman continuum radiation from massive stars could explain the JuMBOs in the ONC. We find that for a range of gas densities the final substellar mass is comfortably within the JuMBO mass range, and that the separations of the JuMBOs are consistent with those of more massive (G- and A-type) binaries, that would have formed from the fragmentation of the cores had they not been photoeroded. The photoerosion mechanism is most effective within the HII region(s) driven by the massive star(s). The majority of the observed JuMBOs lie outside of these regions in the ONC, but may have formed within them and then subsequently migrated due to dynamical evolution.