Star formation from low to high mass: A comparative view

TL;DR

This paper systematically compares low- and high-mass star formation processes, highlighting similarities and differences in physical mechanisms, observational characteristics, and environmental influences, to evaluate the possibility of a unified star formation theory.

Contribution

It provides a comprehensive review identifying regimes of similarity and difference in star formation across mass ranges, and discusses the potential for a unified model.

Findings

Similar gas properties and density structures across regimes

Quantitative differences in outflow, infall, and accretion rates

High-mass stars show increased multiplicity and radiative feedback

Abstract

Star formation has often been studied by separating the low- and high-mass regimes with an approximate boundary at 8M_sun. While some of the outcomes of the star-formation process are different between the two regimes, it is less clear whether the physical processes leading to these outcomes are that different at all. Here, we systematically compare low- and high-mass star formation by reviewing the most important processes and quantities from an observational and theoretical point of view. We identify three regimes where processes are either similar, quantitatively or qualitatively different between low- and high-mass star formation. Similar characteristics can be identified for the turbulent gas properties and density structures of the star-forming regions. Many of the observational characteristics also do not depend that strongly on the environment. Quantitative differences can be found for outflow, infall and accretion rates as well as mean column and volume densities. Also the multiplicity significantly rises from low- to high-mass stars. The importance of the magnetic field for the formation processes appears still less well constrained. Qualitative differences between low- and high-mass star formation relate mainly to the radiative and ionizing feedback that occurs almost exclusively in regions forming high-mass stars. Nevertheless, accretion apparently can continue via disk structures in ionized accretion flows. Finally, we discuss to what extent a unified picture of star formation over all masses is possible and which issues need to be addressed in the future.