The turbulent gas structure in the centers of NGC253 and the Milky Way
  We compare molecular gas properties in the starbursting center of NGC253 and
the Milky Way Galactic Center (GC) on scales of ~1-100 pc using dendograms and
resolution-, area- and noise-matched datasets in CO (1-0) and CO (3-2). We find
that the size-line width relations in NGC253 and the GC have similar slope, but
NGC253 has larger line widths by factors of ~2-3. The $\sigma^2/R$ dependency
on column density shows that, in the GC, on scales of 10-100 pc the kinematics
of gas over $N>3\times10^{21}$ cm$^{-2}$ are compatible with gravitationally
bound structures. In NGC253 this is only the case for column densities
$N>3\times10^{22}$ cm$^{-2}$. The increased line widths in NGC253 originate in
the lower column density gas. This high-velocity dispersion, not
gravitationally self-bound gas is likely in transient structures created by the
combination of high average densities and feedback in the starburst. The high
densities turns the gas molecular throughout the volume of the starburst, and
the injection of energy and momentum by feedback significantly increases the
velocity dispersion at a given spatial scale over what is observed in the GC.
