How Many Infrared Dark Clouds can form Massive Stars and Clusters?

TL;DR

This paper assesses the potential of Infrared Dark Clouds to form massive stars and clusters by establishing a new empirical mass-size threshold, finding most IRDCs fall below this limit and are unlikely to form massive stars without evolution.

Contribution

It introduces a novel empirical mass-size threshold for massive star formation and evaluates IRDCs against this criterion, providing a quantitative assessment of their star-forming potential.

Findings

Most IRDCs fall below the MSF threshold.

IRDCs without significant evolution are unlikely to form massive stars.

A few hundred IRDCs may sustain massive star formation.

Abstract

We present a new assessment of the ability of Infrared Dark Clouds (IRDCs) to form massive stars and clusters. This is done by comparison with an empirical mass-size threshold for massive star formation (MSF). We establish m(r)>870M_sun(r/pc)^1.33 as a novel approximate MSF limit, based on clouds with and without MSF. Many IRDCs, if not most, fall short of this threshold. Without significant evolution, such clouds are unlikely MSF candidates. This provides a first quantitative assessment of the small number of IRDCs evolving towards MSF. IRDCs below this limit might still form stars and clusters of up to intermediate mass, though (like, e.g., the Ophiuchus and Perseus Molecular Clouds). Nevertheless, a major fraction of the mass contained in IRDCs might reside in few 10^2 clouds sustaining MSF.