ALMA CO(3-2) Observations of Star-Forming Filaments in a Gas-Poor Dwarf
  Spheroidal Galaxy
  We report ALMA observations of $^{12}$CO(3-2) and $^{13}$CO(3-2) in the
gas-poor dwarf galaxy NGC 5253. These 0.3"(5.5 pc) resolution images reveal
small, dense molecular gas clouds that are located in kinematically distinct,
extended filaments. Some of the filaments appear to be falling into the galaxy
and may be fueling its current star formation. The most intense CO(3-2)
emission comes from the central $\sim$100 pc region centered on the luminous
radio-infrared HII region known as the supernebula. The CO(3-2) clumps within
the starburst region are anti-correlated with H$\alpha$ on $\sim$5 pc scales,
but are well-correlated with radio free-free emission. Cloud D1, which
enshrouds the supernebula, has a high $^{12}$CO/$^{13}$CO ratio, as does
another cloud within the central 100 pc starburst region, possibly because the
clouds are hot. CO(3-2) emission alone does not allow determination of cloud
masses as molecular gas temperature and column density are degenerate at the
observed brightness, unless combined with other lines such as $^{13}$CO.
