On the Heating Efficiency Derived from Observations of Young Super Star
  Clusters in M82
  Here we discuss the mechanical feedback that massive stellar clusters provide
to the interstellar medium of their host galaxy. We apply an analytic theory
developed in a previous study for M82-A1 to a sample of 10 clusters located in
the central zone of the starburst galaxy M82, all surrounded by compact and
dense HII regions. We claim that the only way that such HII regions can survive
around the selected clusters, is if they are embedded into a high pressure ISM
and if the majority of their mechanical energy is lost within the star cluster
volume via strong radiative cooling. The latter implies that these clusters
have a low heating efficiency, $\eta$, and evolve in the bimodal hydrodynamic
regime. In this regime the shock-heated plasma in the central zones of a
cluster becomes thermally unstable, loses its pressure and is accumulated
there, whereas the matter injected by supernovae and stellar winds outside of
this volume forms a high velocity outflow - the star cluster wind. We
calculated the heating efficiency for each of the selected clusters and found
that in all cases it does not exceed 10% . Such low heating efficiency values
imply a low mechanical energy output and the impact that the selected clusters
provide to the ISM of M82 is thus much smaller than what one would expect using
stellar cluster synthetic models.
