H02 and S05. There are zero starbursting (SFR $\geq  100 $ M$_\sun$ yr$^{-1}$) galaxies with HCN/CO ratios as low as the post-starbursts. This large difference indicates the dense molecular gas fraction in the post-starburst galaxy has changed significantly since the starburst phase. Next, we consider a comparison to H02 and S05’s likely descendants: the early type sample. Drawing from just the early type sample, we find that two galaxies have HCN/CO luminosity ratios as low as the two post-starbursts 16% of the time, thus, these observations alone are not sufficient to distinguish the post-starburst sample from the early types. The post-starburst sample may be already consistent with the early type galaxies, or a separate mechanism could be lowering the dense gas ratio in each (we discuss this further in §\[sec:lowdensegas\]).

So far, we have connected the lack of dense gas to why post-starburst galaxies are not forming stars. Here we explore why the HCN/CO luminosity ratio is low, so we compare to normal star forming galaxies (SFR $< 100$ M$_\sun$ yr$^{-1}$). While the post-starburst galaxies have CO luminosities similar to this comparison sample, the post-starburst SFRs are lower. Comparing the HCN/CO luminosity ratios, the post-starburst galaxies have a lower dense 