Suppression of star formation in dwarf galaxies by grain photoelectric feedback

TL;DR

This study demonstrates that in dwarf galaxies, photoelectric heating by FUV photons plays a dominant role in suppressing star formation, surpassing the effects of supernova feedback, and aligns with observed long gas depletion times.

Contribution

The paper introduces detailed simulations showing that photoelectric heating significantly suppresses star formation in dwarf galaxies, challenging previous assumptions about supernova dominance.

Findings

Photoelectric heating suppresses star formation by over an order of magnitude.

Supernovae alone cannot explain the long gas depletion times.

Photoelectric heating aligns with observed galaxy metallicity effects.

Abstract

Photoelectric heating has long been recognized as the primary source of heating for the neutral interstellar medium. Simulations of spiral galaxies found some indication that photoelectric heating could suppress star formation. However, simulations that include photoelectric heating have typically found that it has little effect on the rate of star formation in either spiral galaxies or dwarfs suggesting that supernovae and not photoelectric heating are responsible for setting the star formation law in galaxies. This result is in tension with recent work indicating that a star formation law that depends on galaxy metallicity, as expected for photoelectric heating but not for supernovae, reproduces the present-day galaxy population better than a metallicity-independent one. Here we report a series of simulations of dwarf galaxies, where the effects of both photoelectric heating and supernovae are expected to be strongest. We simultaneously include space- and time-dependent photoelectric heating, and we resolve the Sedov phase of every supernova blast wave, allowing us to make a direct measurement of the relative importance of momentum injection by supernovae and dust heating by far ultraviolet (FUV) photons in suppressing star formation. We find that supernovae are unable to account for the long observed gas depletion times in dwarf galaxies. Instead, ordinary photoelectric heating is the dominant means by which dwarf galaxies regulate their star formation rate at any given time, suppressing the star formation rate by more than an order of magnitude relative to simulations with only supernovae.