Toward Understanding Massive Star Formation

TL;DR

This review discusses the complex processes of massive star formation, comparing different models and highlighting observational challenges, concluding that it involves unique mechanisms beyond scaled-up low-mass star formation.

Contribution

It provides a comprehensive comparison of competing theories and discusses observational properties, emphasizing the distinct mechanisms in high-mass star formation.

Findings

High-mass star formation involves unique mechanisms beyond scaled-up low-mass processes.

Observations of outflows, multiplicity, and clustering inform theoretical models.

Radiation pressure plays a crucial role in massive star formation dynamics.

Abstract

Although fundamental for astrophysics, the processes that produce massive stars are not well understood. Large distances, high extinction, and short timescales of critical evolutionary phases make observations of these processes challenging. Lacking good observational guidance, theoretical models have remained controversial. This review offers a basic description of the collapse of a massive molecular core and a critical discussion of the three competing concepts of massive star formation: - monolithic collapse in isolated cores - competitive accretion in a protocluster environment - stellar collisions and mergers in very dense systems We also review the observed outflows, multiplicity, and clustering properties of massive stars, the upper initial mass function and the upper mass limit. We conclude that high-mass star formation is not merely a scaled-up version of low-mass star formation with higher accretion rates, but partly a mechanism of its own, primarily owing to the role of stellar mass and radiation pressure in controlling the dynamics.