The Molecular Baryon Cycle of M82
  Baryons cycle into galaxies from the inter-galactic medium, are converted
into stars, and a fraction of the baryons are ejected out of galaxies by
stellar feedback. Here we present new high resolution (3.9"; 68 pc) CO(2-1) and
CO(3-2) images that probe these three stages of the baryon cycle in the nearby
starburst M 82. We combine these new observations with previous CO(1-0) and [Fe
II] images to study the physical conditions within the molecular gas. Using a
Bayesian analysis and the radiative transfer code RADEX, we model molecular
Hydrogen temperatures and densities, as well as CO column densities. Besides
the disc, we concentrate on two regions within the galaxy: an expanding
super-bubble and the base of a molecular streamer. Shock diagnostics,
kinematics, and optical extinction suggest that the streamer is an inflowing
filament, with a molecular gas mass inflow rate of 3.5 M$_\odot$ yr$^{-1}$. We
measure the molecular gas mass outflow rate of the expanding super-bubble to be
17 M$_\odot$ yr$^{-1}$, 5 times higher than the inferred inflow rate, and 1.3
times the star formation rate of the galaxy. The high mass outflow rate and
large star formation rate will deplete the galaxy of molecular gas within eight
million years, unless there are additional sources of molecular gas.
