The formation of low-mass stars and brown dwarfs

TL;DR

This paper reviews the main theories of low-mass star and brown dwarf formation, emphasizing disc fragmentation, and discusses how observations can distinguish between these mechanisms, suggesting multiple processes may contribute.

Contribution

It provides a comparative analysis of formation theories, focusing on disc fragmentation, and highlights observational evidence supporting multiple formation pathways.

Findings

Disc fragmentation addresses key observational constraints.

Observations can help distinguish formation mechanisms.

Multiple formation processes likely contribute to low-mass objects.

Abstract

It is estimated that ~60% of all stars (including brown dwarfs) have masses below 0.2Msun. Currently, there is no consensus on how these objects form. I will briefly review the four main theories for the formation of low-mass objects: turbulent fragmentation, ejection of protostellar embryos, disc fragmentation, and photo-erosion of prestellar cores. I will focus on the disc fragmentation theory and discuss how it addresses critical observational constraints, i.e. the low-mass initial mass function, the brown dwarf desert, and the binary statistics of low-mass stars and brown dwarfs. I will examine whether observations may be used to distinguish between different formation mechanisms, and give a few examples of systems that strongly favour a specific formation scenario. Finally, I will argue that it is likely that all mechanisms may play a role in low-mass star and brown dwarf formation.