Formation of free-floating planetary mass objects via circumstellar disk encounters

TL;DR

This paper proposes a new formation mechanism for free-floating planetary mass objects through tidal bridge fragmentation during circumstellar disk encounters, explaining their abundance and multiplicity in star clusters.

Contribution

It introduces a hydrodynamic simulation-based formation channel for free-floating PMOs via tidal bridge fragmentation, a process not previously detailed.

Findings

Free-floating PMOs can form from tidal bridge fragmentation during disk encounters.

Multiple PMOs can emerge through mutual gravitational capture.

The process is efficient in dense star clusters like Trapezium.

Abstract

The origin of planetary mass objects (PMOs) wandering in young star clusters remains enigmatic, especially when they come in pairs. They could represent the lowest-mass object formed via molecular cloud collapse or high-mass planets ejected from their host stars. However, neither theory fully accounts for their abundance and multiplicity. Here, we show via hydrodynamic simulations that free-floating PMOs have a unique formation channel via the fragmentation of tidal bridges between encountering circumstellar disks. This process can be highly productive in dense clusters like Trapezium forming metal-poor PMOs with disks. Free-floating multiple PMOs also naturally emerge when neighboring PMOs are caught by their mutual gravity. PMOs may thus form a distinct population that is fundamentally different from stars and planets.