Mechanism of Feedback Regulation Within GMCs

Ascertain whether the regulation of the internal states of individual giant molecular clouds by stellar feedback occurs primarily via momentum injection and turbulent forcing within the clouds, via changes in accretion onto the clouds, or via another form of external driving.

Background

By tracking clouds through their evolution, the authors find that ending feedback produces rapid and substantial changes in GMC internal properties, including drops in virial parameter and free-fall time and surges in star formation efficiency. This indicates feedback is an important regulator within individual GMCs.

The precise physical mechanism by which feedback achieves this regulation is unresolved, with candidates including internal momentum injection and turbulent forcing, alterations to accretion rates, or other external driving sources.

References

Whether this is due primarily to momentum injection and turbulent forcing within the clouds themselves, as envisioned by McKee (1989), Matzner (2002), and Krumholz et al. (2006), among others, or whether it is reflects a change in accretion (e.g., Klessen & Hennebelle 2010; Vázquez-Semadeni et al. 2010; Goldbaum et al. 2011) – or another form of external driving – remains to be determined.

— Playing with FIRE: A Galactic Feedback-Halting Experiment Challenges Star Formation Rate Theories  (2406.18526 - Khullar et al., 2024) in Section 3.2.1 (Insights from tracking clouds)

Despite these advances, it is still unclear how feedback couples to dense gas at these small scales, and to what extent it regulates the physical and kinematic properties of individual cores and filamentary structures.

— Dense Cores in the Vicinity of an HII Region  (2608.27913 - Zhang et al., 28 Aug 2026) in Section 1, Introduction