After The Fall: Resolving the Molecular Gas in Post-Starburst Galaxies
  Post-starburst (PSB), or 'E+A', galaxies represent a rapid transitional phase
between major, gas-rich mergers and gas-poor, quiescent early-type galaxies.
Surprisingly, many PSBs have been shown to host a significant interstellar
medium (ISM), despite theoretical predictions that the majority of star-forming
gas should be expelled in AGN- or starburst-driven outflows. To-date, the
resolved properties of this surviving ISM have remained unknown. We present
high resolution ALMA continuum and CO(2$-$1) observations in six gas- and
dust-rich PSBs, revealing for the first time the spatial and kinematic
structure of their ISM on sub-kpc scales. We find extremely compact molecular
reservoirs, with dust and gas surface densities rivaling those found in
(ultra-)luminous infrared galaxies. We observe spatial and kinematic
disturbances in all sources, with some also displaying disk-like kinematics.
Estimates of the internal turbulent pressure in the gas exceed those of normal
star-forming disks by at least 2 orders of magnitude, and rival the turbulent
gas found in local interacting galaxies, such as the Antennae. Though the
source of this high turbulent pressure remains uncertain, we suggest that the
high incidence of tidal disruption events (TDEs) in PSBs could play a role. The
star formation in these PSBs' turbulent central molecular reservoirs is
suppressed, forming stars only 10% as efficiently as starburst galaxies with
similar gas surface densities. "The fall" of star formation in these galaxies
was not precipitated by complete gas expulsion or redistribution. Rather, this
high-resolution view of PSBs' ISM indicates that star formation in their
remaining compact gas reservoirs is suppressed by significant turbulent
heating.
