Spatial Decorrelation of Young Stars and Dense Gas as a Probe of the Star Formation-Feedback Cycle in Galaxies

TL;DR

This study investigates how the spatial decorrelation between dense gas and young stars in galaxies reveals the effects of stellar feedback and star formation processes, using detailed simulations of a dwarf galaxy similar to NGC300.

Contribution

It demonstrates that the decorrelation scale depends on feedback mechanisms and star formation efficiency, providing new insights into the star formation-feedback cycle in galaxies.

Findings

Fiducial simulation matches observed decorrelation in NGC300.

Feedback processes like H2 dissociation and supernovae influence decorrelation scales.

Star formation efficiency per freefall time constrains the correlation and star-forming region lifetimes.

Abstract

The spatial decorrelation of dense molecular gas and young stars observed on $\lesssim 1$ kiloparsec scales in nearby galaxies indicates rapid dispersal of star-forming regions by stellar feedback. We explore the sensitivity of this decorrelation to different processes controlling the structure of the interstellar medium, the abundance of molecular gas, star formation, and feedback in a suite of simulations of an isolated dwarf galaxy with structural properties similar to NGC300 that self-consistently model radiative transfer and molecular chemistry. Our fiducial simulation reproduces the magnitude of decorrelation and its scale dependence measured in NGC300, and we show that this agreement is due to different aspects of feedback, including H$_2$ dissociation, gas heating by the locally variable UV field, early mechanical feedback, and supernovae. In particular, early radiative and mechanical feedback affects the correlation on $\lesssim 100$ pc scales, while supernovae play a significant role on $\gtrsim 100$ pc scales. The correlation is also sensitive to the choice of the local star formation efficiency per freefall time, $\epsilon_{\rm ff}$, which provides a strong observational constraint on $\epsilon_{\rm ff}$ when the global star formation rate is independent of its value. Finally, we explicitly show that the degree of correlation between the peaks of molecular gas and star formation density is directly related to the distribution of the lifetimes of star-forming regions.