The dangers of being trigger--happy

TL;DR

This paper critically evaluates the reliability of observational signposts used to identify triggered star formation, revealing their limited effectiveness and urging caution in interpreting feedback-driven star formation signals.

Contribution

It compares observational indicators with hydrodynamic simulations to assess their accuracy in detecting triggered star formation, highlighting their limited reliability.

Findings

Observational signposts only double the chance of correct identification.

Techniques have limited fidelity in distinguishing triggered from spontaneous star formation.

Caution is advised when interpreting feedback-related star formation signals.

Abstract

We examine the evidence offered for triggered star formation against the backdrop provided by recent numerical simulations of feedback from massive stars at or below giant molecular cloud sizescales. We compile a catalogue of sixty--seven observational papers, mostly published over the last decade, and examine the signposts most commonly used to infer the presence of triggered star formation. We then determine how well these signposts perform in a recent suite of hydrodynamic simulations of star formation including feedback from O--type stars performed by Dale et al (2012a, b, 2013a, b, 2014). We find that none of the observational markers improve the chances of correctly identifying a given star as triggered by more than factors of two at most. This limits the fidelity of these techniques in interpreting star formation histories. We therefore urge caution in interpreting observations of star formation near feedback--driven structures in terms of triggering.