The molecular outflow in NGC253 at a resolution of two parsecs
  We present 0.15'' (~2.5pc) resolution ALMA CO(3-2) observations of the
starbursting center in NGC253. Together with archival ALMA CO(1-0) and CO(2-1)
data we decompose the emission into a disk and non-disk component. We find
~7-16% of the CO luminosity to be associated with the non-disk component
($1.2-4.2 \times 10^7$ K km s$^{-1}$ pc$^2$). The total molecular gas mass in
the center of NGC253 is $\sim 3.6 \times 10^8$ M$_\odot$ with $\sim 0.5 \times
10^8$ M$_\odot$ (~15%) in the non-disk component. These measurements are
consistent across independent mass estimates through three CO transitions. The
high-resolution CO(3-2) observations allow us to identify the molecular outflow
within the non-disk gas. Using a starburst conversion factor, we estimate the
deprojected molecular mass outflow rate, kinetic energy and momentum in the
starburst of NGC253. The deprojected molecular mass outflow rate is in the
range ~14-39 M$_\odot$ yr$^{-1}$ with an uncertainty of 0.4dex. The large
spread arises due to different interpretations of the kinematics of the
observed gas while the errors are due to unknown geometry. The majority of this
outflow rate is contributed by distinct outflows perpendicular to the disk,
with a significant contribution by diffuse molecular gas. This results in a
mass loading factor $\eta = \dot{M}_\mathrm{out} / \dot{M}_\mathrm{SFR}$ in the
range $\eta \sim 8-20$ for gas ejected out to ~300pc. We find the kinetic
energy of the outflow to be $\sim 2.5-4.5 \times 10^{54}$ erg and ~0.8dex
typical error which is ~0.1% of the total or ~8% of the kinetic energy supplied
by the starburst. The outflow momentum is $4.8-8.7 \times 10^8$ M$_\odot$ km
s$^{-1}$ (~0.5dex error) or ~2.5-4% of the kinetic momentum released into the
ISM by feedback. The unknown outflow geometry and launching sites are the
primary source of uncertainty in this study.
