Ionization--induced star formation IV: Triggering in bound clusters

TL;DR

This study investigates how ionizing feedback from massive stars influences star formation in bound clouds, revealing complex effects on efficiency, stellar distribution, and morphology, with implications for understanding triggered star formation.

Contribution

It provides a detailed simulation-based analysis of ionization-induced star formation, highlighting the nuanced impacts on star formation efficiency, mass functions, and cloud structures.

Findings

Feedback reduces star formation efficiency.

Stellar mass functions shift towards lower masses.

Gas structures like pillars are linked to star formation processes.

Abstract

We present a detailed study of star formation occurring in bound star--forming clouds under the influence of internal ionizing feedback from massive stars across a spectrum of cloud properties. We infer which objects are triggered by comparing our feedback simulations with control simulations in which no feedback was present. We find feedback always results in a lower star--formation efficiency and usually but not always results in a larger number of stars or clusters. Cluster mass functions are not strongly affected by feedback, but stellar mass functions are biased towards lower masses. Ionization also affects the geometrical distribution of stars in ways that are robust against projection effects, but may make the stellar associations more or less subclustered depending on the background cloud environment. We observe a prominent pillar in one simulation which is the remains of an accretion flow feeding the central ionizing cluster of its host cloud and suggest that this may be a general formation mechanism for pillars such as those observed in M16. We find that the association of stars with structures in the gas such as shells or pillars is a good but by no means foolproof indication that those stars have been triggered and we conclude overall that it is very difficult to deduce which objects have been induced to form and which formed spontaneously simply from observing the system at a single time.