  The Milky Way galaxy is surrounded by a circumgalactic medium (CGM) that may
play a key role in galaxy evolution as the source of gas for star formation and
a repository of metals and energy produced by star formation and nuclear
activity. The CGM may also be a repository for baryons seen in the early
universe, but undetected locally. The CGM has an ionized component at
temperatures near $2 \times 10^{6}$~K studied primarily in the soft X-ray band.
Here we report a survey of the southern Galactic sky with a soft X-ray
spectrometer optimized to study diffuse soft X-ray emission. The X-ray emission
is best fit with a disc-like model based on the radial profile of the surface
density of molecular hydrogen, a tracer of star formation, suggesting that the
X-ray emission is predominantly from hot plasma produced via stellar feedback.
Strong variations in the X-ray emission on angular scales of $\sim10^{\circ}$
indicate that the CGM is clumpy. Addition of an extended, and possibly massive,
halo component is needed to match the halo density inferred from other
observations.
