Why is the gas in "post-starburst" galaxies not forming stars?

10 August 2021

Though galaxies can largely be classified as either “star-forming” or “quiescent”, depending on the rate of new stars being formed, a subset of galaxies are understood to have recently experienced a burst of formation followed by a rapid halt. Are these “post-starburst” galaxies objects transitioning from star-forming to quiescent? Why are they no longer forming stars?

The initial assumption is that the answer to the latter question is that post-starburst galaxies lack the fuel (i.e., gas) to form new stars. But observations in recent years have shown this to not be the case – post-starburst galaxies often possess significant amounts of gas. Why is it not forming stars?

In “After The Fall: Resolving the Molecular Gas in Post-Starburst Galaxies” (Smercina+), we map the gas in a sample of post-starburst galaxies to better understand the physical properties. This detailed mapping shows that the gas reservoirs are physically compact, and that the gas may be highly turbulent, suppressing star formation.

The article has been submitted to the AAS Journals and a preprint is available.