Modes of star formation from Herschel

TL;DR

Herschel surveys reveal that star formation in nearby regions is largely governed by cloud fragmentation, but this simple model may not apply in extreme environments like the Galactic center, where different physical processes dominate.

Contribution

The paper synthesizes Herschel survey results to propose a unified view of star formation driven by cloud fragmentation, highlighting exceptions in extreme galactic environments.

Findings

Starless core distribution mirrors young stellar objects in nearby regions.

Cloud fragmentation influences the initial mass function and star formation rate.

Scaling laws may need revision in the Galactic center environment.

Abstract

We summarize some of the results obtained from Herschel surveys of the nearby star forming regions and the Galactic plane. We show that in the nearby star forming regions the starless core spatial surface density distribution is very similar to that of the young stellar objects. This, taken together with the similarity between the core mass function and the initial mass function for stars and the relationship between the amount of dense gas and star formation rate, suggest that the cloud fragmentation process defines the global outcome of star formation. This "simple" view of star formation may not hold on all scales. In particular dynamical interactions are expected to become important at the conditions required to form young massive clusters. We describe the successes of a simple criterion to identify young massive cluster precursors in our Galaxy based on (sub-)millimetre wide area surveys. We further show that in the location of our Galaxy where the best candidate for a precursor of a young massive cluster is found, the "simple" scaling relationship between dense gas and star formation rate appear to break down. We suggest that in regions where the conditions approach those of the central molecular zone of our Galaxy it may be necessary to revise the scaling laws for star formation.