Remarks on Rapid vs. Slow Star Formation

TL;DR

This paper argues that star formation occurs rapidly rather than slowly, challenging traditional views, by analyzing observational data and theoretical considerations about molecular cloud lifetimes and star formation processes.

Contribution

It provides a critique of long-lived protostellar core models and supports a rapid star formation scenario based on observational and theoretical arguments.

Findings

Protostellar cores do not have long lifetimes before collapsing.

Spiral arm widths do not imply extended star formation periods.

Rapid star formation is more consistent with observations and theory.

Abstract

We discuss problems with some observational estimates indicating long protostellar core lifetimes and large stellar age spreads in molecular clouds. We also point out some additional observational constraints which suggest that protostellar cores do not have long lifetimes before collapsing. For external galaxies, we argue that the widths of spiral arms does not imply a long star-formation process, since the formation of massive stars will disrupt molecular clouds, move material around, compress it in other regions which produce new star-forming clouds. Thus, it seems unavoidable that this cyclical process will result in an extended period of enhanced star formation, which does not represent the survival time of any individual molecular cloud. We argue that the rapid star formation indicated observationally is also easier to understand theoretically than the traditional scenario of slow quasi-static contraction with ambipolar diffusion.